Russian negotiators at peace talks in Istanbul demanded Ukraine pull its troops out of all the Ukrainian regions claimed by Moscow before they would agree to a ceasefire, a senior Ukrainian official familiar with the talks told Reuters.

That demand, along with others the Ukrainian official said were made at Friday's talks, went beyond the terms of a draft peace deal that the United States proposed last month after consultations with Moscow.

The talks in Istanbul, the first direct contacts between the two sides in three years, ended with agreement for a prisoner exchange but failed to agree to a ceasefire. A Ukrainian source had said on Friday the Russians had made conditions he described as "non-starters", without giving details.

At a briefing with reporters on Saturday, Kremlin spokesman Dmitry Peskov was asked about the terms that, according to the Ukrainian official, Moscow put forward, but he declined to comment, saying the discussions need to take place behind closed doors.

The Ukrainian official, who spoke on condition of anonymity to reveal details of the talks, said Russian proposed the following terms for a peace deal:

* The withdrawal of Ukrainian troops from the Donetsk, Zaporizhzhia, Kherson and Luhansk regions of Ukraine, only after which there can be a ceasefire. The regions are largely or partially controlled by Russian forces, but Ukrainian troops are still fighting to hold on to the remaining parts of the regions. There was no such demand in the draft deal prepared by the United States.

* International recognition that five parts of Ukraine — the Crimea peninsula annexed in 2014, as well as the Donetsk, Luhansk, Kherson and Zaporizhzhia regions — are Russian. The US draft had proposed only US de jure recognition for Crimea, and US de facto recognition for Russian-controlled parts of the other regions.

* Ukraine becomes a neutral state, has no weapons of mass destruction, and Kyiv's allies will not station any of their troops on Ukrainian soil. This demand was absent from the US proposal.

* All sides in the conflict renounce their claims to receive compensation for war damages. The US proposal had stipulated that Ukraine receives compensation.

According to the Ukrainian official, Russian negotiators transmitted those demands verbally, and did not share any document containing their terms.

Ukraine has already said the Russian negotiating position in Istanbul showed it was not serious about peace. Kyiv's European allies are now pressing US President Donald Trump to impose new sanctions on Russia.

The head of the Russian delegation at the talks expressed satisfaction with the meeting, and said Moscow was willing to keep talking to Kyiv.

The US draft peace proposal from April was prepared after Trump envoy Steve Witkoff flew to Moscow for rounds of talks with Russian President Vladimir Putin.

Kyiv and European allies drafted an alternative proposal, which stated there should be a ceasefire first so negotiations could start, and deferred any discussion of territory until later.