US President Donald Trump said there would be"very serious consequences" if his Russian counterpart Vladimir Putin did not agree to a ceasefire in the Ukraine conflict at a meeting scheduled for Friday in Alaska.

After meetings with several European leaders, Trump also said he wants to use Friday's meeting to"quickly schedule a second meeting" that includes Ukrainian President Volodymyr Zelenskiy, after being pressured by allies to do so.

"There's a very good chance we'll have a second meeting that will be more productive than the first," Trump told reporters at the Kennedy Center, as quoted by Bloomberg, adding that he"is laying the groundwork for a second meeting."

Trump responded to calls from European allies to include the Ukrainian leader in the talks, after Zelensky was excluded from the summit, which will take place at a military base in Anchorage, Alaska's largest city.

Earlier, Trump also sought to allay fears that he might accept terms for a ceasefire that would be detrimental to Ukraine without taking Ukraine's position into account, by talking about"territorial swaps" in recent days.

French President Emmanuel Macron said Trump had pledged to respect the principle that any deal involving the ceding of territory would have to have the agreement of Ukrainian officials and that he was"very clear that the US wants to achieve a ceasefire at this meeting in Alaska."

Trump and US Vice President JD Vance held video calls for about an hour with the leaders of Germany, France, Poland, and Italy, as well as Zelensky, NATO Secretary General Mark Rutte, and European Commission President Ursula von der Leyen, who wrote on social media that the leaders had"a very good call" and that it "reinforced the consensus on Ukraine."