Russian leader Vladimir Putin will for the first time hold formal talks with Ukrainian counterpart Volodymyr Zelensky over the conflict in Ukraine's east on Monday, in a much-anticipated summit in Paris.

No comprehensive peace deal is expected from the afternoon meeting -- mediated by French President Emmanuel Macron and German Chancellor Angela Merkel -- but diplomats hope that the exercise will help to boost trust between the two men.

Thousands have been killed and one million have fled their homes since pro-Russia militias in eastern Ukraine launched a bid for independence in 2014 -- kicking off a conflict that deepened Russia's estrangement from the West.

The separatists seized control of Donetsk and Lugansk regions shortly after Russia's annexation of Crimea, a Ukrainian peninsula.

Diplomats have emphasised that the issue of Crimea -- a seizure that gave Putin a popularity boost but led to international sanctions being imposed -- is not on the table at the summit.

Kiev has made clear its determination to never give up the peninsula, which the international community still regards as part of Ukraine.

The Kremlin has sent signals that it is ready to work with Zelensky, who Putin has described as "likeable" and "sincere".

But Putin also will not want to return empty-handed and will be pushing for an easing of sanctions.

- 'Problem of trust' -

German Foreign Minister Heiko Maas told the Funke newspaper group ahead of the summit "we have to do everything we can... to make progress in the Ukrainian peace process", and described the conflict as "a festering wound in Europe".

Maas praised Zelensky for bringing "new momentum" to the talks, adding that "to make progress with the next difficult steps, Russia needs to make a move too".

The goals of Monday's meeting include agreeing to disband illegal militias, the departure of foreign fighters from Donetsk and Lugansk and Ukraine taking back control over its border with Russia, according to a French presidential source.

"There remains the problem of trust between the parties. This needs to be created before we can move forward," said the source, who asked not to be named.

Also key is agreeing a calendar for elections to be held in Donetsk and Lugansk under Ukrainian law with the two regions enjoying special status -- an idea known as the Steinmeier Formula.

"If the summit meeting is to be meaningful, it should have a result, and the result should very much be on the Steinmeier Formula," said Gerhard Mangott, professor of international relations at Austria's Innsbruck University.

"It remains to be seen whether Ukraine is willing to give up some of its pre-conditions for implementing the Steinmeier Formula."

- 'Wound of war' -

Monday's meeting is the first such summit in three years and seeks to implement accords signed in Minsk in 2015 that call for the withdrawal of heavy weapons, the restoration of Kiev's control over its borders, wider autonomy, and the holding of local elections.

The French presidential source said it was not just Putin's strategic calculations that had impeded the implementation of the Minsk accords but also the "difficulties in Ukraine due to public opinion, divisions and the fundamental wound caused by the war."

The summit is a hugely delicate event for everyone involved, but particularly for Zelensky, who is under pressure not to cede ground to the Kremlin.

For Macron, the summit is a centrepiece of an increasingly bold foreign policy he is driving despite troubles at home, where transport workers have been on strike for days in a dispute over pension reforms.

Macron, who shocked NATO allies this year by declaring the alliance brain dead, has made clear his belief that Europe needs a strategic partnership with Russia.