Russian President Vladimir Putin and Ukrainian leader Volodymyr Zelensky are likely to have a one-on-one meeting during four-way summit talks in Paris next month, the Kremlin said Wednesday.

Putin and Zelensky plan to join French President Emmanuel Macron and German Chancellor Angela Merkel on December 9 for a summit aimed at resolving the five-year conflict in eastern Ukraine, where Moscow-backed separatists have carved out breakaway statelets.

Putin's top foreign adviser Yury Ushakov said Wednesday that a separate meeting between the Russian and Ukrainian leaders was likely on the cards, too.

"It appears that a separate meeting will be held," Ushakov said, Russian news agencies reported, while adding that the programme of the summit was still being finalised.

A Ukrainian diplomatic source, when asked about the possibility of the one-on-one, told AFP: "We still don't know."

Speaking to reporters in the Lithuanian capital Vilnius, Zelensky said he was ready for meetings with every state leader present at the Paris summit, if necessary.

The United States voiced solidarity with Ukraine and called on Russia to implement a 2015 plan that called both for a ceasefire and political resolution of the conflict.

"Our support for Ukraine's sovereignty is unwavering, and we are committed to working with our Allies and partners to keep pressure on Russia to live up to its commitments," Secretary of State Mike Pompeo said in a statement.

Russian President Vladimir Putin and his Ukrainian counterpart Volodymyr Zelensky may meet for the first time in Paris
Russian President Vladimir Putin and his Ukrainian counterpart Volodymyr Zelensky may meet for the first time in Paris AFP / Tiziana FABI

State Department spokeswoman Morgan Ortagus praised the "prudent but difficult steps towards peace and reform" taken by Zelensky.

The 41-year-old former comedian came to power in May on the back of pledges to bring peace while regaining control of the breakaway regions.

But Zelensky has yet to meet with Putin, 67.

The encounter would attempt to end a conflict which saw pro-Moscow separatists declare unrecognised breakaway republics in the Ukrainian eastern regions of Donetsk and Lugansk and has left more than 13,000 dead since 2014.

Zelensky said in Vilnius he did not expect the war to end tomorrow.

"But as president of Ukraine, I want a clear understanding when and how we can stop this war," he said.

Ukraine and its Western allies accuse Moscow of giving financial and military backing to separatists, which Russia denies.

The summit has been held up by numerous obstacles that highlight the difficulty of resolving the conflict.

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