Ukrainian and Russian negotiators will tackle the vital issue of territory during two days of talks in Abu Dhabi starting on Friday, each side said, with no sign of a softening of their positions to end the four-year war.

Ukraine is under mounting US pressure to reach a peace deal in the war triggered by Russia’s full-scale invasion in February 2022, with Moscow demanding Kyiv cede its entire eastern industrial area of Donbas before it stops fighting.

Ukrainian President Volodymyr Zelenskiy said the territorial dispute would be a top priority of the next round of talks in the United Arab Emirates.

“The question of Donbas is key. It will be discussed how the three sides..., see this in Abu Dhabi today and tomorrow,” he said, responding to questions in a WhatsApp media chat a day after talks with US President Donald Trump at the World Economic Forum in Davos that both leaders described as positive.

The talks in the Gulf were due to begin on Friday evening, a Zelenskiy aide said, and resume on Saturday morning.

Russian President Vladimir Putin’s demand that Ukraine surrender the 20% it still holds of the Donetsk region of the Donbas - about 5,000 sq km (1,900 sq miles) - has proven a major stumbling block to a breakthrough deal. Zelenskiy refuses to give up land that Russia has not been able to capture in four years of grinding, attritional warfare.

Kremlin spokesman Dmitry Peskov said on Friday that Russia’s insistence on Ukraine yielding the Donbas was “a very important condition”.

A source close to the Kremlin told Reuters that Moscow considers a so-called “Anchorage formula”, which Moscow said was agreed between Trump and Putin at a summit last August, to mean Russia controlling all of Donbas and freezing the current front lines elsewhere in Ukraine’s east and south.

Donetsk is one of four Ukrainian regions Moscow said in 2022 it was annexing after referendums rejected by Kyiv and Western nations as bogus. Most countries recognise Donetsk as part of Ukraine. Putin says Donetsk is “historical” Russian territory.

Security guarantees agreed, Zelenskiy says

Zelenskiy said on Thursday in Davos that the Abu Dhabi talks would be the first trilateral meetings involving Ukrainian and Russian envoys and US mediators since the war began.

Last year Russia and Ukrainian delegations had their first face-to-face meeting since 2022 when they met in Istanbul. A top Ukrainian military intelligence officer also had talks with US and Russian delegations in Abu Dhabi in November.

Russian Admiral Igor Kostyukov, head of Russia’s military intelligence agency, was heading Moscow’s team in Abu Dhabi. Ukraine’s delegation was to be led by Rustem Umerov, secretary of Kyiv’s National Security and Defence Council.

Zelenskiy also told reporters that a deal on US security guarantees for Kyiv was ready, and that he was only waiting on Trump for a specific date and place to sign it.

Ukraine has sought robust security guarantees from Western allies in the event of a peace deal to prevent Russia, which has shown little interest in ending the war, from invading again.

For its part, Russia has floated the idea of using the bulk of nearly $5 billion of Russian assets frozen in the United States to fund a recovery of Russian-occupied territory inside Ukraine. Ukraine, backed by European allies, demands that Russia pay it reparations.

Asked about Russia’s idea, Zelenskiy dismissed it as “nonsense”. He added: “Of course, we will fight (to use these assets for Ukraine), and it is absolutely fair regarding the use of all frozen assets (by Ukraine).”

Ukraine is enduring its harshest winter of the war as Russia inflicts heavy missile and drone strikes on its energy infrastructure. With temperatures well below freezing, hundreds of thousands of people in Kyiv and other cities have suffered long power cuts and been left without heating.

Ukraine cites Russia’s escalating attacks on its energy grid as evidence that Putin has no real interest in peace.

Russia says it wants a diplomatic solution but will keep working to achieve its goals by military means as long as a negotiated solution remains elusive.