Donald Trump has accused Volodymyr Zelensky of harming peace negotiations over the war in Ukraine with "inflammatory statements".

The Ukrainian president told a news conference on Tuesday that Kyiv would not recognise Russian control of Crimea, comments which Trump said "would do nothing but prolong" the conflict.

The US president's remarks on his social media platform Truth Social came after Vice-President JD Vance said the US would "walk away" from its deal making role if the two sides did not come to an agreement.

US officials pulled out of a London meeting this week to focus on talks in Moscow, as the pace of diplomacy to end the war quickens.

A key part of the US proposal to end the conflict, according to leaks in recent days, involves recognising Crimea – which was annexed illegally by Russia in 2014 – as de jure Russian territory.

"There's nothing to talk about here. This is against our constitution," Zelensky said.

In response, Trump said: "This statement is very harmful to the peace negotiations with Russia", adding that it would prolong the "killing field".

"It's inflammatory statements like Zelensky's that makes it so difficult to settle this war," Trump said.

"Stopping the killing is task number one," Zelensky said on social media on Wednesday.

The comments are the latest chapter in an often fractious relationship between the two leaders.

In February, the pair clashed in a fiery meeting in the Oval Office.

Trump repeatedly said on the campaign trail he could end the Ukraine-Russia war in one day, but as he approaches his 100th day in office a truce remains elusive, appearing to wear thin the patience of the White House.

Vance told reporters this week during a visit to India: "It's time for them to either say yes or for the US to walk away from this process."

"We've engaged in an extraordinary amount of diplomacy, of on the ground work, he said.

Vance said a deal between Russia and Ukraine would likely require both countries "to have to give up some of the territory they currently own".

London talks between officials from the UK, France, Germany, Ukraine and the US aimed at securing a ceasefire were downgraded this week after US Secretary of State Marco Rubio and special envoy Steve Witkoff pulled out.

Instead, Trump's Ukraine envoy, Gen Keith Kellogg, is attending the talks in London and Witkoff will be headed to Russia to meet with President Vladimir Putin for the fourth time.

British diplomats said they were not entirely clear why Rubio and Witkoff had pulled out of the London talks.

The US state department blamed logistical reasons, but it was clear the decision was last-minute and left the Foreign Office wrongfooted.

There is growing speculation that Russia might be willing to halt its invasion along current front lines in return for significant concessions.

However, there is little clarity about where the latest talks are heading or whether they will succeed.

Russia intensified its attacks on Ukraine on Wednesday, after a brief lull over Easter when it halted air strikes.

Nine people were killed and dozens more wounded in the eastern Ukrainian city of Marhanets when a Russian drone hit a bus carrying workers.

All this comes amid a report in the Financial Times that Russia might be ready to halt its invasion along existing front lines and give up territorial claims to areas it does not currently occupy, in return for US recognition of Russian sovereignty over Crimea.

Kremlin spokesman Dmitry Peskov rejected the report, telling state media that "a lot of fakes are published nowadays".

Zelensky said no such proposals had been shared with him and he rejected recognising Crimea as Russian territory.

Recognising Russia's illegal annexation of Crimea would not only be politically impossible for Zelensky to accept, it would also be contrary to post-war international legal norms that borders should not be changed by force.

Speaking to BBC Radio 4's Today programme, Yuriy Sak, an adviser to Ukraine's ministry of strategic industries, said it was "not productive to discuss" such reports and added it was "naïve" to expect Ukraine to change its position on "non-negotiable" issues such as Crimea.

Sak added that Ukrainian negotiators would attend the London meeting on a "very clear, narrow mandate" to achieve a ceasefire that will "pave the way for further talks".

Putin called a temporary ceasefire for the Easter weekend but UK Defence Secretary John Healey told the House of Commons on Tuesday that British military intelligence had found no evidence of a let-up in attacks.

"While Putin has said he declared an Easter truce, he broke it," he said. "While Putin says he wants peace, he has rejected a full ceasefire and while Putin says he wants to put an end to the fighting, he continues to play for time in the negotiations."

It is estimated that hundreds of thousands of people have been killed or injured on all sides since Russia invaded Ukraine on 24 February 2022, and nearly seven million Ukrainians are currently listed as refugees worldwide.

The conflict goes back more than a decade, to 2014, when Ukraine's pro-Russian president was overthrown. Russia then annexed Crimea and backed militants in bloody fighting in eastern Ukraine.