Confirmation hearings for President-elect Donald Trump's picks for his cabinet and other high-ranking administration positions got under way on Tuesday, with defense secretary nominee Pete Hegseth the first to face questioning from U.S. senators.

Several confirmation hearings are scheduled before Trump, a Republican, is sworn in as president on Monday, while others will not be held until after he takes office.

Nominees require a simple majority in the 100-seat Senate to be confirmed. Republicans hold 53 seats, but some of Trump's picks could struggle to be confirmed if a small number of Republicans oppose their nominations.

Here are Trump's choices for some of the key posts including defense, intelligence, health, diplomacy, trade, justice, immigration and economic policymaking.

PETE HEGSETH, DEFENSE SECRETARY

Hegseth, 44, is a military veteran who has expressed disdain for the "woke" policies of Pentagon leaders, including its top military officer.

As secretary of defense, Hegseth could make good on Trump's campaign promise to rid the U.S. military of generals whom he accuses of pursuing progressive policies on diversity in the ranks that conservatives have railed against.

It could also set up a collision course between Hegseth and the chairman of the Joint Chiefs of Staff, Air Force General C.Q. Brown, whom Hegseth accused of "pursuing the radical positions of left-wing politicians."

Hegseth, a former Fox News commentator, denied in his confirmation hearing allegations made in a police report that he sexually assaulted a woman in 2017 at a conference in California. No charges were filed, and he entered into a private settlement with the alleged victim, but the allegations are complicating his confirmation prospects. He has also in the past opposed women in combat roles but walked back that stance during the hearing on Tuesday.

KRISTI NOEM, HOMELAND SECURITY SECRETARY

As homeland security secretary, Noem would oversee a sprawling federal agency of 260,000 employees that handles everything from border protection to cybersecurity to transportation safety and disaster response.

The current governor of South Dakota, Noem, 53, rose to national prominence after refusing to impose a statewide mask mandate during the pandemic. Noem's confirmation hearing is scheduled to begin on Wednesday.

PAM BONDI, ATTORNEY GENERAL

Trump picked former Florida Attorney General Bondi on the day his previous choice, Matt Gaetz, withdrew from consideration in the face of opposition from Senate Republicans over allegations of sexual misconduct and illicit drug abuse.

Bondi, 59, was the top law enforcement officer of the country's third most populous state from 2011 to 2019. She served on Trump's Opioid and Drug Abuse Commission during his first administration.

Trump's inner circle has described the attorney general as the most important member of the administration after Trump himself, key to his plans to carry out mass deportations, pardon Jan. 6, 2021 rioters, and seek retribution against those who prosecuted him over the past four years.

Bondi has been a defender of Trump's false claims that he lost the 2020 election due to widespread voter fraud. The first of two scheduled confirmation hearings for Bondi begins on Wednesday.

MARCO RUBIO, SECRETARY OF STATE

If confirmed, Rubio, a U.S. senator, would be the first Latino to serve as the nation's top diplomat.

Rubio, 53, was arguably the most hawkish option on Trump's short list for the post. The Florida-born senator has advocated in the past for a muscular foreign policy with respect to U.S. geopolitical foes, including China, Iran and Cuba.

Over the last several years, he has softened some of his stances to align more closely with Trump's views. Trump has accused past presidents of leading the U.S. into costly and futile wars and has pushed for a less interventionist foreign policy.

Rubio is set to appear before the Senate Foreign Relations Committee on Wednesday.

JOHN RATCLIFFE, CIA DIRECTOR

Ratcliffe, who was director of national intelligence at the end of Trump's first term, would helm the Central Intelligence Agency in his second administration.

A former congressman and prosecutor, Ratcliffe, 59, is seen as a Trump loyalist who could likely win Senate confirmation.

Still, during his time as director of national intelligence, Ratcliffe often contradicted the assessments of career civil servants, drawing criticism from Democrats who said he politicized the role to curry favor with Trump.

Ratcliffe's confirmation hearing is scheduled for Wednesday.

SEAN DUFFY, TRANSPORTATION SECRETARY

Duffy, a former U.S. congressman from Wisconsin and Fox News host, would oversee aviation, automotive, rail, transit and other transportation policies at the department with about a $110-billion budget, as well as significant funding that remains under the Biden administration's 2021 $1-trillion infrastructure law and EV-charging stations.

Trump has vowed to reverse the Biden administration's vehicle emissions rules, which have spurred automakers to build more electric vehicles.

Duffy, 53, first became known as a cast member on MTV's "The Real World" reality show in the late 1990s. Duffy's confirmation hearing is scheduled for Wednesday.

CHRIS WRIGHT, ENERGY SECRETARY

Wright, a top Trump donor, is the founder and CEO of Liberty Energy, an oilfield services firm based in Denver.

The 59-year-old is a promoter of fossil fuels and has been skeptical that extreme weather events are tied to climate change.

As Trump's energy secretary, he would, among other things, oversee the nation's nuclear stockpile. Wright also would serve on the new National Energy Council. His confirmation hearing is scheduled for Wednesday.

RUSS VOUGHT, OFFICE OF MANAGEMENT AND BUDGET DIRECTOR

Vought, a key architect of Project 2025, a conservative plan to overhaul the government, will return as director of an agency that helps determine the president's policy priorities and how to pay for them.

Vought, 48, who was OMB chief during Trump's 2017-2021 term, will play a major role in setting budget priorities and implementing Trump's campaign promise to roll back government regulations. His confirmation hearing is scheduled for Wednesday.

DOUG BURGUM, INTERIOR SECRETARY AND 'ENERGY CZAR'

Burgum, 68, a wealthy former software company executive, has portrayed himself as a traditional, business-minded conservative. He ran against Trump for the Republican presidential nomination before quitting and becoming a supporter.

The Interior Department manages public lands and minerals, national parks and wildlife refuges. The department also carries out the U.S. government's trust responsibility to Native Americans.

As chair of a new National Energy Council, Burgum is expected to coordinate with several agencies to boost oil and gas output, particularly with regard to drilling on government-owned land. Burgum's confirmation hearing is set for Thursday.

LEE ZELDIN, EPA ADMINISTRATOR

Zeldin, a former congressman from New York state and a staunch Trump ally, would take over as administrator of the Environmental Protection Agency with a mandate to slash environmental regulations.

Zeldin, 44, served in Congress from 2015 to 2023. In 2022, he lost the New York governor's race to Democratic incumbent Kathy Hochul.

Trump has promised to overhaul U.S. energy policy, with the aim of maximizing the country's already record-high oil and gas production by rolling back regulations and speeding up permitting.

Zeldin's confirmation hearing is scheduled for Thursday.

SCOTT TURNER, HOUSING AND URBAN DEVELOPMENT SECRETARY

Turner, 52, a former Texas state legislator and National Football League player, would take over the Department of Housing and Urban Development if confirmed.

He was the first executive director of the White House Opportunity and Revitalization Council during Trump's first term, a role in which he helped the country's distressed communities, Trump said in a statement.

Turner's confirmation hearing is scheduled for Thursday.

SCOTT BESSENT, TREASURY SECRETARY

As Trump's Treasury secretary, Bessent would hold vast influence over economic, regulatory and international affairs.

A longtime hedge fund investor who taught at Yale University for several years, Bessent, 62, has a warm relationship with the president-elect.

While Bessent has long favored free-market policies popular in the pre-Trump Republican Party, he has also spoken highly of Trump's use of tariffs as a negotiating tool. He has praised the president-elect's economic philosophy, which rests on a skepticism of both regulation and international trade.

Bessent's confirmation hearing is scheduled for Thursday.

KASH PATEL, FBI DIRECTOR

Patel, who during Trump's first term advised both the director of national intelligence and the defense secretary, has been a fierce critic of the FBI. He has previously called for it to be stripped of its intelligence-gathering role and for the firing of any employee who refuses to support Trump's agenda.

A former Republican House staffer, Patel, 44, frequently appeared on the campaign trail to rally support for Trump during his presidential bid.

The FBI's current director, Christopher Wray, a Republican first appointed by Trump, announced in December that he will resign his post this month. Patel's confirmation hearing has yet to be scheduled.

TULSI GABBARD, DIRECTOR OF NATIONAL INTELLIGENCE

Gabbard, a former Democratic member of Congress and an officer in the U.S. Army Reserve, was appointed by Trump to serve as director of national intelligence, where she would oversee 18 agencies tasked with intelligence gathering.

Gabbard, 43, has been an outspoken critic of the Biden administration's foreign policy, particularly with regard to its support of Ukraine in the war with Russia.

Her confirmation hearing has yet to be scheduled.

HOWARD LUTNICK, COMMERCE SECRETARY

The co-chair of Trump's transition effort and the longtime chief executive of financial services firm Cantor Fitzgerald, Lutnick has been picked to head the Commerce Department, the agency that has become the U.S. weapon of choice against China's tech sector.

A bombastic New Yorker like Trump, Lutnick, 63, has uniformly praised Trump's economic policies, including his use of tariffs.

Trump said Lutnick also would be given "additional direct responsibility" for the Office of U.S. Trade Representative. His confirmation hearing has not been scheduled.

ROBERT F. KENNEDY, JR., HEALTH AND HUMAN SERVICES SECRETARY

Kennedy, 70, an environmental activist who has spread misinformation about the dangers of vaccines, is now poised to lead the top U.S. health agency.

A former independent presidential candidate, he has suggested he would gut the 18,000-employee Food and Drug Administration, which ensures the safety of food, drugs and medical devices, and replace hundreds of employees at the National Institutes of Health.

Kennedy has decried the U.S. food industry for adding ingredients that he says have made Americans less healthy.

The Department of Health and Human Services oversees the FDA, the Centers for Disease Control and Prevention, the National Institutes of Health and the massive Medicare and Medicaid programs, which provide health coverage for the poor, those aged 65 and older, and the disabled.

Trump said in an interview with Time in December that he will be talking to Kennedy about the future of childhood vaccination programs, citing high autism rates in children. Kennedy has asserted a debunked link between vaccines and autism.

A former family babysitter has alleged that Kennedy groped her 25 years ago. No charges were filed, and Kennedy has said he does not recall the incident. His confirmation hearing has yet to be scheduled.

LORI CHAVEZ-DEREMER, LABOR SECRETARY

Trump's pick of Chavez-DeRemer, a former U.S. congresswoman from Oregon, could be one of the rare selections who draws bipartisan support.

Chavez-DeRemer, 56, is considered one of the most union-friendly Republicans in Congress, and her selection was viewed as a way for Trump to reward union members who voted for him.

The pick was praised by Teamsters President Sean O'Brien, while some conservatives expressed dismay. Her confirmation hearing has yet to be scheduled.

BROOKE ROLLINS, AGRICULTURE SECRETARY

As agriculture secretary, Rollins, the 52-year-old president of the America First Policy Institute, would be in charge of a 100,000-person agency whose remit includes farm and nutrition programs, forestry, and agricultural trade.

The institute is a right-leaning think tank whose personnel have worked closely with Trump's campaign to help shape policy for his incoming administration. She was the acting director of the Domestic Policy Council during Trump's first term. Her confirmation hearing is not yet scheduled.

LINDA MCMAHON, EDUCATION SECRETARY

McMahon is a former executive CEO of World Wrestling Entertainment who served as the chief of the Small Business Administration during Trump's first term.

As education secretary, she would oversee an agency that Trump has pledged to eliminate.

It may be more likely, however, that McMahon, 76, works to further conservative education policy goals, including doing away with diversity programs in public schools and allowing tax dollars to be used for private school tuition.

Her confirmation hearing is yet to be scheduled.

ELISE STEFANIK, AMBASSADOR TO THE UNITED NATIONS

Stefanik, a U.S. representative from New York state and staunch Trump supporter, would serve as his ambassador to the United Nations and function as the United States' voice on that body.

Stefanik, 40, the former House of Representatives' Republican conference chair, took a leadership position in the House in 2021 when she was elected to replace then-Representative Liz Cheney, who was ousted for criticizing Trump's false claims of election fraud.

Stefanik will arrive at the U.N. after bold promises by Trump to end the Russia-Ukraine war and Israel's war in Gaza.

Her confirmation hearing is yet to be scheduled.

MARTIN MAKARY, HEAD OF THE FOOD AND DRUG ADMINISTRATION

Trump nominated Makary to lead the FDA, the world's most influential drug regulator with a more than $7-billion budget.

Makary, a surgeon and public policy researcher at Johns Hopkins University, raised concerns about a number of public health issues during the pandemic, touting protection from natural immunity while opposing vaccine mandates for the general public. His Senate hearing is yet to be scheduled.

DAVE WELDON, DIRECTOR OF THE CENTERS FOR DISEASE CONTROL AND PREVENTION

Weldon, a 71-year-old former congressman and medical doctor, is Trump's choice for director of the Centers for Disease Control and Prevention, a sweeping agency with a $17.3-billion budget charged with protecting the nation's health. His confirmation hearing has not been scheduled.

JANETTE NESHEIWAT, U.S. SURGEON GENERAL

Nesheiwat, a director of a New York chain of urgent care clinics and Fox News contributor, would serve as U.S. surgeon general.

Nesheiwat treated patients during the pandemic, tended to victims of Hurricane Katrina and the Joplin tornado, and has worked for the Samaritan's Purse disaster relief organization providing care in Morocco, Haiti and Poland, Trump said. Her confirmation hearing has not been scheduled.

TODD BLANCHE, DEPUTY ATTORNEY GENERAL

Blanche, 50, a former New York federal prosecutor who represented Trump in several of his recent legal cases, would serve as deputy attorney general if confirmed, the No. 2 job at the Justice Department which carries out many of the day-to-day managerial duties at the agency. His confirmation hearing has not been scheduled.

JAMIESON GREER, U.S. TRADE REPRESENTATIVE

As U.S. trade representative, Greer would have a key role in executing Trump's sweeping tariff agenda that promises to upend global trade.

Greer, a 44-year-old trade lawyer, served as chief of staff to Trump's former U.S. trade representative, Robert Lighthizer, the architect of Trump's original tariffs on some $370 billion worth of Chinese imports during Trump's first White House term. His confirmation hearing has not been scheduled.

MIKE WALTZ, NATIONAL SECURITY ADVISER

Waltz, a Republican U.S. representative and a retired Army Green Beret, has been a leading critic of China.

A Trump loyalist who also served in the National Guard as a colonel, Waltz, 50, has criticized Chinese military activity in the Asia-Pacific and voiced the need for the U.S. to be ready for a potential conflict in the region.

The national security adviser is an influential role that does not require Senate confirmation. Waltz will be responsible for briefing Trump on key national security issues and coordinating with different agencies.

ELON MUSK AND VIVEK RAMASWAMY, HEADS OF THE DEPARTMENT OF GOVERNMENT EFFICIENCY

Outspoken tech billionaire Elon Musk and former Republican presidential candidate Vivek Ramaswamy have been charged with leading a newly created Department of Government Efficiency, a reward for their staunch support during the campaign.

Trump said Musk, 53, and Ramaswamy, 39, will offer proposals to reduce government bureaucracy, slash excess regulations, cut waste and restructure federal agencies, although the panel will hold no actual authority under federal law. Instead, the panel will work with the White House and the Office of Management and Budget, Trump has said. The panel is not a government department, and Musk and Ramaswamy will not face Senate hearings.

TOM HOMAN, 'BORDER CZAR'

Homan has been tasked with one of Trump's biggest campaign priorities: securing the nation's borders. Trump made cracking down on migrants in the country illegally a central element of his campaign, promising mass deportations.

As "border czar," Homan, 62, has said he would prioritize deporting immigrants illegally in the U.S. who posed safety and security threats as well as those working at job sites.

Homan served as the acting director of Immigration and Customs Enforcement during Trump's first administration. He does not need Senate confirmation.

SUSIE WILES, CHIEF OF STAFF

Wiles, one of Trump's two campaign managers, will be his White House chief of staff, likely making her one of the most powerful women in government.

The 67-year-old longtime Florida Republican political operative is credited with running an efficient campaign that helped Trump make inroads with new voters. Supporters hope she will instill a sense of order and discipline that was often lacking during Trump's first four-year term, when he cycled through a number of chiefs of staff. The chief of staff does not need Senate confirmation.