US President Donald Trump said he believes he could meet "very soon" with Russian President Vladimir Putin to discuss ending the war in Ukraine.
Speaking to reporters, Mr Trump said he was working hard to achieve peace, and said he believes both Mr Putin and Ukrainian President Volodymyr Zelensky want to stop fighting.
His comments come as the US and Russia are preparing for initial talks in Saudi Arabia in the coming days.
US Secretary of State Marco Rubio said Ukraine and Europe would be part of any "real negotiations" to end Moscow's war, signaling that US talks with Russia this week were a chance to see how serious Mr Putin is about peace.
America's top diplomat played down European concerns of being cut out of the initial talks between Russia and the US set to take place in Saudi Arabia in the coming days.
In an interview with CBS, Mr 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, Reuters reported that US 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," Mr Rubio said on CBS.
"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."
Read more: Ukraine appears sidelined after Trump-Putin phone call
US Middle East envoy Steve Witkoff and National Security Adviser Mike Waltz were due to leave for Saudi Arabia this evening, Mr Witkoff said in a Fox News interview.
Mr 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 finalised, he said.
The planned talks in Saudi Arabia coincide with a US bid to cut a deal with Kyiv to open up Ukraine's natural resources wealth to US investment.
Mr Zelensky questioned if minerals in areas held by Russia would be given to Mr Putin.
European role in peace talks
Mr Rubio and Mr Witkoff rejected concerns that Ukraine and other European leaders would have no place at peace negotiations, despite Mr Trump's Ukraine envoy, Keith Kellogg, suggesting precisely that at this weekend's Munich Security Conference.
Mr Witkoff noted that Ukrainian officials had met several US officials in recent days at the conference, while Mr Trump had talked with Mr Zelensky last week.
Mr 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," Mr Rubio said.
"We're just not there yet."
French President Emmanuel Macron will host European leaders tomorrow for an emergency summit on the Ukraine war, his office said, in the wake of Mr Kellogg's remarks.
European officials have been left shocked and flat-footed by the Trump administration's moves on Ukraine, Russia and European defence in recent days.
Chief among their fears is that they can no longer count on US military protection and that MrTrump will attempt to ink a Ukraine peace deal with Mr 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, Mr Rubio declined to provide confirmation, saying only that they "did not go into any details."
After the call, Russia said that the two had discussed the removal of "unilateral barriers" set by the previous US administration in relations with Russia.
Mr Rubio said he did address the "difficult" operating conditions of the US embassy in Russia with Mr Lavrov.
If there was to be progress in Ukraine peacemaking, both Russia and the US would need properly functioning embassies in the other country, he added.
