President Donald Trump on Tuesday ruled out sending US troops to back up any Ukraine peace deal but suggested air support instead, as European nations began hashing out security guarantees ahead of a potential Russia summit.

In a flurry of diplomacy aimed at ending the war, Trump brought Ukrainian President Volodymyr Zelensky and European leaders to the White House on Monday, three days after his landmark encounter with Russia's Vladimir Putin in Alaska.

But while Trump said Putin had agreed to meet Zelensky and accept some Western security guarantees for Ukraine, those promises have been met with extreme caution by Kyiv and Western capitals, and many details remain vague.

Putin proposed holding the summit with Zelensky in Moscow, three sources familiar with the Trump call told AFP. One source said Zelensky immediately said no to meeting in the capital of his country's invader.

Trump, long a fierce critic of the billions of dollars in US support to Ukraine since Russia invaded in 2022, said that European nations were "willing to put people on the ground" to secure any settlement.

"France and Germany, a couple of them, UK, they want to have boots on the ground," Trump said in a Fox News interview. 

"We're willing to help them with things, especially, probably, if you talk about by air."

Asked what assurances Trump had that US boots would not be on the ground, he replied: "Well, you have my assurance and I'm president."

Allies discuss next steps

The White House later doubled down on Trump's statements -- but gave few new details on either the summit or the security guarantees.

Press Secretary Karoline Leavitt told reporters that Trump "has definitively stated US boots will not be on the ground in Ukraine" and that the use of US air power was "option and a possibility." 

Leavitt insisted that Putin had promised Trump he would meet Zelensky, and said top US officials were "coordinating" with Russia on a summit.

Trump had dramatically interrupted his meeting with Zelensky and the Europeans at the White House on Monday to call the Russian leader.

Allies have expressed doubts that Putin will go through with the meeting.

The Europeans are however seizing on the possibility of a peace deal following the Trump talks.

French President Emmanuel Macron and British Prime Minister Keir Starmer brought together around 30 of Ukraine's allies known as the "Coalition of the Willing" for virtual consultations.

Starmer told them coalition teams and US officials would meet in the coming days to "prepare for the deployment of a reassurance force if the hostilities ended," a Downing Street spokesperson said.

The military chiefs of staff of all 32 nations in the NATO military alliance will meet by video Wednesday to discuss Ukraine, officials said.

Geneva, Budapest floated for summits

Russia has warned that any solution must also protect its own "security interests" and has ruled out Ukraine joining NATO.

Foreign Minister Sergei Lavrov added that any meeting between the leaders "must be prepared very thoroughly."

Lavrov's comments, and Putin's offer of Moscow as a summit venue, reinforced European fears that Russia was once again stalling. 

Macron said he wanted the summit to take place in Geneva, a historic venue for peace talks.

Switzerland said it was ready to offer immunity to Putin, who faces an arrest warrant from the International Criminal Court over the war.

Macron and German Chancellor Friedrich Merz have both said the summit could take place in two weeks.

The White House declined to comment on a Politico report that it was eying Hungary's capital Budapest as a venue for a follow-up three-way summit including Trump.

On the streets of Kyiv, there was skepticism about whether the latest talks can end the grinding conflict.

"The main problem is Putin himself doesn't want it," said Anton, 32, who works in a warehouse.

But in Moscow, some people were more optimistic. "I hope we can agree on mutually beneficial terms," said Vyacheslav, 23, who works for the government. 

by Shaun Tandon and Danny Kemp