Ukraine is preparing to present a revised peace plan to the White House, as it seeks to avoid making territorial concessions to Russia.
Kyiv is set propose alternatives to the US after President Volodymyr Zelensky again ruled out surrendering land, saying he had 'no right' to do so under Ukrainian or international law.
He made the comments as he met European and Nato leaders on Monday, part of a collective push to deter the US from backing a peace deal which includes major concessions for Ukraine, and which allies fear would leave it vulnerable to a future invasion.
Meanwhile, the city of Sumy in north-western Ukraine was left without power overnight after a Russian drone attack.
The region's governor said more than a dozen drones had hit power infrastructure, the latest in Russia's nightly attacks. No deaths were reported.
Zelensky's ongoing diplomatic tour of Europe comes after days of intensive talks between US and Ukrainian negotiators over the weekend, that failed to produce a deal Kyiv could agree to.
Zelensky was due to be briefed on that private summit on Monday by his chief aide Rustem Umerov, who wrote on Telegram that he would feed back details of direct talks between the US and Russian President Vladimir Putin.
The Ukrainian president told a news conference that his team could send a new proposal to the Americans as soon as Tuesday, AFP news agency reported.
On the subject of surrendering land, Zelensky said: 'Russia is insisting that we give up territories, but we don't want to cede anything.'
He continued: 'We have no legal right to do so, under Ukrainian law, our constitution and international law. And we don't have any moral right either.'
Zelensky has long maintained that any changes to Ukraine's borders would need to be authorised by a public referendum.
Elsewhere, he told reporters that the initial 28-point plan proposed by the US - and rejected by Kyiv and European leaders as being too favourable to Russia - had been cut down to 20 points, according to Interfax-Ukraine news agency.
He said no 'pro-Ukrainian' points had been removed from the draft, though there had also been no 'compromise' on the subject of territory.
Zelensky singled out control of the eastern Donbas region and the Zaporizhzhia nuclear power plant as being among the 'most sensitive' issues.
The original leaked version of the US-backed plan proposed that Ukraine hand over total control of the Donbas to Russia, despite the fact that Kremlin forces have been unable to capture it in full after almost four years of war.
Energy produced at Zaporizhzhia, the largest nuclear power plant in Europe, would be split between Russia and Ukraine, the draft plan said.
Leaders in Kyiv and across Europe have indicated there has been progress in refining that draft in recent weeks, and have praised the Trump administration for seeking to mediate an end to the fighting.
But Monday's hastily arranged Downing Street summit - attended by Zelensky, UK Prime Minister Sir Keir Starmer, French President Emmanuel Macron, and German Chancellor Friedrich Merz - was widely viewed as a show of support for Ukraine as it seeks to resist White House pressure.
No 10 said there had been an agreement that the US-led talks represented a 'critical moment' to ramp up support for Ukraine, and repeated calls for a 'just and lasting peace... which includes robust security guarantees'.
The nature of those future security guarantees are another open question in the negotiations.
Efforts continue to assemble an international coalition prepared to offer ongoing military support to Kyiv in the event of a peace deal, though it is not yet clear what form that would take.
While the UK and France have proposed deploying international troops in Ukraine, several key defence players in Europe, including Germany and Italy, have expressed scepticism about that idea.
It is also not clear to what extent the US would be willing to underpin any future defence arrangements for Ukraine.
Following talks in London, Zelensky flew to Brussels to meet Nato chief Mark Rutte and EU chief Ursula von der Leyen, and will meet Prime Minister Georgia Meloni in Italy on Tuesday.
Moscow has also claimed talks with the White House have been constructive, despite little public indication it has moved on any of the goals set out by the Kremlin when it launched its full-scale invasion in February 2022.
On Sunday, Trump indicated that he viewed Zelensky as the main obstacle to securing a peace deal, something he has made a key foreign policy goal and which the president claimed he would be able to achieve rapidly during the 2024 presidential election campaign.
He told reporters that Russia was 'fine' with the peace plan outlined to both sides by the US, but that he was a 'little disappointed that President Zelensky hasn't read it'. It was unclear whether that was the case.
