Zelensky met Starmer in London on Thursday / AFP

US President Donald Trump on Thursday acknowledged his high-stakes summit with Vladimir Putin may fail, and said any Ukraine deal would come through a future three-way meeting with Kyiv to "divvy things up."

Russian President Vladimir Putin flies to Alaska on Friday at the invitation of Trump in his first visit to a Western country since he ordered the 2022 invasion of Ukraine that has killed tens of thousands of people.

The Kremlin said that the two presidents planned to meet one-on-one, heightening fears by European leaders that Putin will cajole Trump into a settlement imposed on Ukraine.

Trump, on the eve of the summit, insisted that he would not finalize any deal with Putin and that he would include Ukrainian President Volodymyr Zelensky in any decisions.

"This meeting sets up the second meeting, but there is a 25 percent chance that this meeting will not be a successful meeting," Trump told Fox News Radio.

"The second meeting is going to be very, very important, because that's going to be a meeting where they make a deal. And I don't want to use the word 'divvy' things up. But you know, to a certain extent, it's not a bad term," Trump said.

Zelensky has refused any territorial concessions to Russia, which has ramped up attacks and made sharp gains on the battlefield just ahead of the summit.

Secretary of State Marco Rubio said any future deal needed to ensure Ukraine's security.

"To achieve peace, I think we all recognize that there'll have to be some conversation about security guarantees," Rubio told reporters in Washington, saying he was "hopeful" about the summit.

Trump has previously ruled out letting Ukraine join NATO and backed Russia's stance that Kyiv's aspirations to enter the transatlantic alliance triggered the war.

Ukraine and most of its European allies reject Putin's narrative and point to his remarks denying the historical legitimacy of Ukraine.

- Shifting Trump tone -

Trump had boasted that he could end the war within 24 hours of returning to the White House in January.

But his calls to Putin -- and intense pressure on Zelensky to accept concessions -- have failed to move the Russian leader and Trump has warned of "very severe consequences" if Putin keeps snubbing his overtures.

Putin on Thursday welcomed US efforts to end the conflict and said that talks could also help yield an agreement on nuclear arms control.

"The US administration... is making quite energetic and sincere efforts to end the fighting," Putin told a meeting of top officials in Moscow.

The talks are set to begin at 11:30 am (1930 GMT) Friday at the Elmendorf Air Force Base, a major US military installation in Alaska that has been crucial in monitoring Russia.

"This conversation will take place in a one-on-one format, naturally with the participation of interpreters," Kremlin aide Yuri Ushakov told reporters in Moscow.

He said that delegations would continue discussions over a working lunch and that Putin and Trump would hold a joint news conference. 

The White House has not confirmed any plans for a joint press appearance.

Trump faced heated criticism over his joint news conference after his 2018 summit with Putin in Helsinki where he sided with Russia over US intelligence in accepting Putin's denials of interfering in the 2016 US election to help Trump.

- European support for Zelensky -

Zelensky, who will not join Friday's summit in Alaska, met Thursday with British Prime Minister Keir Starmer, after talks a day earlier in Berlin.

Starmer greeted the Ukrainian leader with a warm hug and handshake on the steps of his Downing Street residence and later voiced solidarity.

European leaders expressed relief after a call with Trump on Wednesday, saying he appeared focused on a ceasefire rather than concessions by Ukraine.

A day before the summit, Ukraine fired dozens of drones at Russia, wounding several people and sparking fires at an oil refinery in the southern city of Volgograd.

Russia meanwhile said its troops had captured two new settlements in eastern Ukraine, where it has been advancing for months.

Diplomacy since Russia's invasion has largely failed to secure agreements beyond swaps of prisoners.

Russia said Thursday it had returned 84 prisoners to Ukraine in exchange for an equal number of Russian POWs in the latest exchange.

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