President Volodymyr Zelensky says trilateral talks on ending the war in Ukraine are to take place with Russia and the US in the United Arab Emirates, after he met President Donald Trump in Davos.

As the diplomatic pace appeared to intensify, Trump said his meeting with Zelensky was good, and US envoy Steve Witkoff headed to Moscow for talks with Russia's Vladimir Putin.

Witkoff, who was travelling to Moscow with Trump's son-in-law Steve Kushner, said he was optimistic about a deal.

"I think we've got it down to one issue and we have discussed iterations of that issue, and that means it's solvable," he said before leaving the Swiss resort.

Trump's envoy gave no details about the remaining sticking point, but Zelensky later clarified that the future status of eastern Ukraine remained the unsolved issue.

He made clear that the planned talks in the Emirates would involve Russia as well as the US and Ukraine, adding that "the Russians have to be ready for compromises, not only Ukraine".

"It's all about the land. This is the issue which is not solved yet," Zelensky told reporters at the World Economic Forum in Davos, Switzerland - adding that trilateral talks might provide the two sides with "variants".

The US proposal for the Ukraine's industrial heartland in Donbas is for a demilitarised and free economic zone in exchange for security guarantees for Kyiv.

"If both sides want to solve this, we're going to get it solved," Witkoff said, explaining that he would be heading to Abu Dhabi after Moscow, where working groups would be covering military issues as well as economic prosperity.

Zelensky also told reporters that he had reached agreement with Trump on future US security guarantees for Ukraine in the event of a deal. He gave no details but said it would need to go before the US Congress and Ukrainian parliament before signing.

Although he said the "Coalition of the Willing", led by the UK and France, had committed forces on the ground to monitor the deal, he was adamant a Trump backstop would be necessary too: "No security guarantees work without the US."

The Ukrainian president had travelled through the night to get to Davos.

He had initially called off his trip to deal with the aftermath of Russian strikes on Kyiv's power infrastructure, which have left large areas of the capital without heating, water or power during the harshest winter so far in almost four years of Russia's full-scale war. Thousands of apartment blocks remain without heating.

Zelensky said last month that a 20-point US plan to end the war was 90% ready and that Ukraine's position on Donbas, in eastern Ukraine, was different to Russia's.

As part of the US 20-point plan, Zelensky has offered to withdraw troops from the 25% of Donetsk region that Ukraine still controls by up to 40km (25 miles), to create an economic zone in Donbas, if Russia does the same. 

Kremlin spokesman Dmitry Peskov said on Thursday that discussions with the American envoys would continue "on the Ukrainian issue and other related topics" and refused to say whether he shared Witkoff's optimism on achieving a deal.

Putin is known to covet control of the entire region, and Russian forces have advanced slowly in the east in the past year.

Another big sticking point that Zelensky highlighted last month was future control of Ukraine's enormous Zaporizhzhia nuclear plant, seized by Russia in March 2022.

Zelensky joked that he hoped the Emirates knew about the planned meeting, but in a measure of the seriousness of the talks he named some his most senior officials in the Ukrainian team taking part.

The head of the country's national security and defence council, Rustem Umerov, was already talking to US officials in Davos, along with Kyrylo Budanov, the head of Zelensky's office, and negotiator David Arakhamia. They will be joined the chief of the general staff, Andrii Hnatov.