Britain's King Charles will press the importance of unity with the United States and the need to defend democratic values in an address to Congress on Tuesday at a time of deep divisions between the two countries over the war in Iran.
Charles and Queen Camilla are on a four-day state visit to the US designed to underscore the ties forged between Britain and its former colony over the 250 years since independence, known in recent decades as the "special relationship".
The king will steer clear of the political acrimony between President Donald Trump and British Prime Minister Keir Starmer but underline their countries' shared values as the duty to promote peace, compassion and democracy, while protecting the environment and religious freedom.
A palace source said that, despite the periodic differences in the two countries' relationship, the king will say: "Time and again, our two countries have always found ways to come together."
The long-planned visit has unfolded against tensions over the US-Israeli war on Iran, after Trump repeatedly criticised Britain for declining to support the offensive, and after an internal Pentagon email suggested Washington could review its support for Britain's claim to the Falkland Islands.
The king's address, scheduled to begin at 3pm EDT (1900 GMT), will be the second by a British sovereign to the US Congress. His mother, Queen Elizabeth II, spoke to both houses in 1991.
It is a central event of the state visit - the most high-profile of Charles' reign - and will be followed by a state dinner on Tuesday night.
Deep bonds
The speech is set to last about 20 minutes, the source said.
It will focus on the deep bonds between the two nations and how the alliance can benefit global security and prosperity, but it will also voice some caution about the US going it alone, and refer to NATO and Ukraine.
Trump's administration has repeatedly criticised many of the US-led military alliance's other members for not offering more assistance to US military operations against Iran and pressed European countries into sharing more of the financial burden for supporting Ukraine against Russia's invasion.
The king will also touch on his pride at having served in the Royal Navy and deep defence, intelligence and security ties - ties that have been strained by Trump's criticism of Britain's military capabilities.
While written on the advice of the British government, much of the language and tone comes from Charles himself, the source said.
The British government hopes the visit will shore up the transatlantic relationship by appealing to Trump, a vocal admirer of the British royal family who often calls Charles a "great man".
Charles will also reference the shooting at the White House Correspondents' Association dinner on Saturday.
The visit began on Monday when Charles and Camilla met Trump and first lady Melania Trump for a private tea at the White House, followed by a garden party at the British ambassador’s residence, where they mingled with media leaders, Washington socialites and US officials.
On Wednesday, the royals will be in New York City to commemorate those killed in the attacks of September 11, 2001, and the trip concludes in Virginia on Thursday with the king meeting people involved in conservation, reflecting his long-standing environmental advocacy.
He will then travel to Bermuda.
