The Kremlin said on Thursday that Russia had reiterated its invitation for Ukrainian President Volodymyr Zelenskyy to ​come to Moscow for peace talks, as U.S.-led ‍efforts to reach a deal to end the nearly four-year war in Ukraine intensify.

Washington-mediated peace talks in Abu Dhabi last weekend have injected some new momentum into efforts to clinch a peace deal, but profound differences persist between the Russian and Ukrainian negotiating stances. Fierce fighting is still raging, while Kyiv battles debilitating power outages caused by recent missile strikes.

An unnamed U.S. official told Axios on Saturday that Zelenskyy and Russian President Vladimir Putin were "very close" to setting up a meeting after the U.S.-mediated talks.

A new round of Abu Dhabi talks between Russian and Ukrainian negotiating delegations is scheduled for Sunday, and U.S. President Donald Trump - who is pushing for a deal to end Europe's biggest conflict since World War Two - said on Tuesday that "very good things" were happening in the process.

Major disagreements remain though, including over who gets what territory in any deal, the potential presence of international peacekeepers or monitors in post-war Ukraine, and the fate of the Russian-controlled Zaporizhzhia nuclear power plant.