U.S. Secretary of State Marco Rubio on Sunday said Ukraine and Europe would be part of any "real negotiations" to end Moscow's war, signaling that U.S. talks with Russia this week were a chance to see how serious Russian President Vladimir Putin is about peace.

America's top diplomat played down European concerns of being cut out of the initial talks between Russia and the United States set to take place in Saudi Arabia in the coming days. In an interview with CBS, Rubio said a negotiation process had not yet begun in earnest, and if talks advanced, the Ukrainians and other Europeans would be brought into the fold.

Earlier on Sunday, Reuters reported that U.S. officials had handed European officials a questionnaire asking, among other things, how many troops they could contribute to enforcing a peace agreement between Ukraine and Russia.

"President Trump spoke to Vladimir Putin last week, and in it, Vladimir Putin expressed his interest in peace, and the president expressed his desire to see an end to this conflict in a way that was enduring and that protected Ukrainian sovereignty," Rubio said on CBS's "Meet the Press."

"Now, obviously it has to be followed up by action, so the next few weeks and days will determine whether it's serious or not. Ultimately, one phone call does not make peace."

U.S. Middle East envoy Steve Witkoff and national security adviser Mike Waltz were due to leave for Saudi Arabia on Sunday evening, Witkoff said in a Fox News interview.

Rubio noted he was due to be in Saudi Arabia anyway due to previously arranged official travel. The composition of the Russian delegation had not yet been finalized, he said.

The planned talks in Saudi Arabia coincide with a U.S. bid to cut a deal with Kyiv to open up Ukraine's natural resources wealth to U.S. investment. Ukrainian President Volodymyr Zelenskiy, in an NBC interview broadcast on Sunday, questioned if minerals in areas held by Russia would be given to Putin.

Trump, who held a call with Putin on Wednesday and said the Russian leader wants peace, said Sunday he was confident Putin would not want to try and take control of the entirety of Ukraine.

"That would have caused me a big problem, because you just can't let that happen. I think he wants to end it," Trump told reporters in West Palm Beach, Florida.

Trump added that Zelinskiy would be involved in the conversations to end the conflict.

EUROPEAN ROLE IN PEACE TALKS, OR NOT?

Rubio and Witkoff rejected concerns that Ukraine and other European leaders would have no place at peace negotiations, despite Trump's Ukraine envoy, Keith Kellogg, suggesting precisely that at this weekend's Munich Security Conference.

Witkoff noted in an interview on Fox News' "Sunday Morning Futures" that Ukrainian officials had met several U.S. officials in recent days at the conference, while Trump had talked with Zelenskiy last week.

Rubio, for his part, said that Ukrainians and other Europeans would be included in any meaningful negotiations.

"Ultimately, it will reach a point - if it's real negotiations, and we're not there yet - but if that were to happen, Ukraine will have to be involved because they're the ones that were invaded, and the Europeans will have to be involved because they have sanctions on Putin and Russia as well," Rubio said.

"We're just not there yet."

French President Emmanuel Macron will host European leaders on Monday for an emergency summit on the Ukraine war, Macron's office said, in the wake of Kellogg's remarks.

European officials have been left shocked and flat-footed by the Trump administration’s moves on Ukraine, Russia and European defense in recent days.

Chief among their fears is that they can no longer count on U.S. military protection and that Trump will attempt to ink a Ukraine peace deal with Putin that undermines Kyiv and broader European continental security.

Asked if he had discussed lifting sanctions on Russia during a Saturday phone call with Russian Foreign Minister Sergei Lavrov, Rubio declined to provide confirmation, saying only that they "did not go into any details."

After the call, Moscow said that the two had discussed the removal of "unilateral barriers" set by the previous U.S. administration in relations with Russia.

Rubio said he did address the "difficult" operating conditions of the U.S. embassy in Moscow with Lavrov. If there was to be progress in Ukraine peacemaking, both Russia and the U.S. would need properly functioning embassies in the other country, he added.