In Moscow, Kremlin spokesman Dmitry Peskov told Russian news agencies preparations were underway for a conversation between Russian President Vladimir Putin and Trump.

The talks in Turkey on Friday were the first time the sides had held face-to-face talks since March 2022, weeks after Russia's full-scale invasion of its smaller neighbour.

A senior Ukrainian official familiar with the talks said Russian negotiators demanded Ukraine pull its troops out of all Ukrainian regions claimed by Moscow before they would agree to a ceasefire.

Trump, writing on Truth Social, said he would speak with Putin to discuss stopping the war at 10 a.m. Eastern (2 p.m. GMT) on Monday.

"THE SUBJECTS OF THE CALL WILL BE, STOPPING THE 'BLOODBATH' THAT IS KILLING, ON AVERAGE, MORE THAN 5000 RUSSIAN AND UKRAINIAN SOLDIERS A WEEK, AND TRADE," he wrote.

He said he would speak afterward with Ukrainian President Volodymyr Zelenskiy and various members of NATO.

"Hopefully it will be a productive day, a ceasefire will take place, and this very violent war, a war that should have never happened, will end."

Trump had offered to travel to Turkey for the talks while in the Gulf last week if Putin would also attend, but Putin sent a team of negotiators instead.

The president has been pressuring Putin and Zelenskiy to agree to a ceasefire in the more than three-year-old war.

The Kremlin declined to comment on the terms that Russia had put forward at Friday's meeting. The talks lasted only one hour and 40 minutes and yielded an agreement to trade 1,000 prisoners of war on each side. The two countries have not specified when that would happen.

Zelenskiy called on Saturday for stronger sanctions on Moscow after a Russian drone killed nine bus passengers in the Sumy region of northeastern Ukraine. "This was a deliberate killing of civilians," he said.

"Pressure must be exerted on Russia to stop the killings. Without tougher sanctions, without stronger pressure, Russia will not seek real diplomacy."

Russia, which denies targeting civilians, said it struck a military target in Sumy. Its defence ministry said Russian troops had captured another settlement in eastern Ukraine.

Russian Foreign Minister Sergei Lavrov spoke by telephone with US Secretary of State Marco Rubio and said he welcomed the "positive role" of the US in helping to secure a resumption of talks between Russia and Ukraine. A Russian foreign ministry statement quoted Lavrov as saying contacts would continue.

Rubio was quoted as telling the CBS news program Face the Nation that Lavrov said the Russians were "working on a series of ideas and requirements that they would have in order to move forward with a ceasefire and further negotiations."

"I think your question is, 'Are they tapping us along?'" he said in the interview to be broadcast on Sunday. "Well, that's what we're trying to find out."

Rubio, who told reporters earlier in Rome that the Vatican could be a venue to facilitate further Russia-Ukraine dialogue, told CBS it was a "very generous offer that may be taken up on."

Ukraine and Western governments, including the US, have demanded Russia agree to an immediate, unconditional ceasefire lasting at least 30 days. But the Ukrainian source said Moscow's negotiators had demanded the withdrawal of Ukrainian troops from the Donetsk, Zaporizhzhia, Kherson and Luhansk regions of Ukraine, with a ceasefire to take place only after that.

The source said that and other demands went beyond the terms of a draft peace deal that the United States proposed last month after consultations with Moscow.

Peskov declined to comment on the Ukrainian account, saying talks should be conducted "absolutely behind closed doors".

He said the next steps would be to carry out the prisoner exchange and conduct further work between the two sides. Peskov said it was possible that Putin could meet Zelenskiy, but only if "certain agreements" were reached, which he did not specify.

Zelenskiy had challenged Putin earlier in the week to meet him in person, an offer the Russian leader ignored.

Turkish President Tayyip Erdogan said his country, after hosting the talks, was resolved to continue its mediation role.