Russian and Ukrainian negotiators met in Abu Dhabi on Friday for peace talks, with no compromise made on a vital territorial issue.

The U.S. has been pressuring Ukraine to reach a peace deal with Russia, as the latter country demands that it receive the Donbas region, Reuters reported.

Ukrainian President Volodymyr Zelensky said that the territorial dispute would be a crucial point of the peace talks in the United Arab Emirates, as the military conflict between the neighboring countries reaches the four-year mark next month. 

"The question of Donbas is key. It will be discussed how the three sides ... see this in Abu Dhabi today and tomorrow," Zelensky told reporters in a WhatsApp chat.

His comment comes after talks with President Trump on Thursday at the World Economic Forum in Davos yielded no immediate results.

Zelensky's aide said the negotiations in the UAE are expected to continue on Saturday morning.

The talks come amid intensified Russian strikes on Ukraine's energy system that have cut power and heating to major cities like Kyiv, with temperatures below freezing.

Kremlin spokesman Dmitry Peskov said Friday that Russia's demand that Ukraine yield the Donbas is "a very important condition."