Russian President Vladimir Putin expressed support for a U.S. ceasefire proposal to halt Russia’s war with Ukraine but stressed that details would have to be worked out.

“We agree with the proposals to halt the fighting, but we proceed from the assumption that the ceasefire should lead to lasting peace and remove the root causes of the crisis,” Putin told reporters Thursday in Moscow.

“Maybe I should call President [Donald] Trump and have a discussion with him,” he said.

At the White House, Trump said it would be “very disappointing” if Russia rejected U.S. efforts to end the fighting.

“We would like to see a ceasefire from Russia,” Trump told reporters. “A lot of the details of a final agreement have actually been discussed. Now we’re going to see if Russia is there and, if not, it will be a very disappointing moment for the world.”

Earlier, Putin’s top foreign policy aide dismissed the United States’ 30-day ceasefire proposal, saying it would merely provide Ukraine’s military with a temporary respite from fighting.

His comments came after U.S. special envoy Steve Witkoff arrived in Moscow to meet with Russian officials on the ceasefire proposal. In his comments, Russian presidential aide Yuri Ushakov confirmed he has been in regular contact with U.S. national security adviser Mike Waltz and said they agreed these contacts would remain confidential.

U.S. officials met earlier this week with Ukrainian officials in Saudi Arabia to present the ceasefire plan.

Ukrainian President Volodymyr Zelenskyy welcomed the U.S. effort, saying Wednesday that Ukraine is “ready for a ceasefire for 30 days as proposed by the American side.”

Zelenskyy said the halt in fighting could be used to create a broader peace deal for the conflict, which began with Russia’s February 2022 full-scale invasion of Ukraine.

The talks in Moscow come as the Russian Defense Ministry said Thursday its forces have retaken control of Sudzha, a major town in Russia’s western Kursk region, from Ukrainian troops.

Ukrainian forces had taken the town during a surprise attack on the Kursk region bordering Ukraine last August and had been struggling to hold it ever since.

Some information for this report came from The Associated Press, Agence France-Presse and Reuters.