Donald Trump has claimed that Russia and Ukraine have agreed to an "energy ceasefire", with Kyiv saying it would support such a move but Moscow yet to comment, BBC reports.
The US president insisted that it was "effective immediately" but provided no details.
Ukrainian President Volodymyr Zelensky initially expressed surprise at the announcement, before saying Kyiv would support it if Moscow did. He also accused Russia of striking Ukrainian energy facilities after Trump's post.
Trump has been urging Ukraine to stop strikes on Russian oil infrastructure - which Kyiv says are vital to curtailing revenue for Moscow's war machine - so Russia can fulfil a recently-struck deal to release diesel to the US and the global market.
The diesel deal, temporarily undoing sanctions on Russian imports, is attracting growing criticism. Zelensky called it a gift to Russian President Vladimir Putin. European officials and some US politicians, including from Trump's Republican party, have said they do not support it.
The deal is Trump's latest effort to lower domestic fuel prices ahead of the midterm elections, having spent months grappling with the political consequences of the war with Iran which has pushed up global fuel prices, particularly those for diesel.
That has soured Trump's standing with the American public, who have been stung by the higher pump prices and knock-on effects that led to across-the-board inflation.
Zelensky said it was "news" to him that an energy truce was in effect, before writing on social media that his officials "look forward to clear details of America's dialogue with Russia".
"Ukraine is ready not to strike at Russian energy and we count on Russia's similar readiness and on the agreement of the president of the United States of America on this," he said.
The BBC has asked the White House for further details.
UK Prime Minister Andy Burnham said Britain "strongly supports President Trump's call today for a sustained energy ceasefire to start now", while France, Canada and the EU also expressed support.
