Russian leader Vladimir Putin will hold formal talks for the first time with his Ukrainian counterpart Volodymyr Zelensky over the conflict in Ukraine's east, at a highly 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 the exercise will help to bolster 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 the Donetsk and Lugansk regions shortly after Russia's annexation of the Ukrainian peninsula of Crimea. The seizure gave Mr Putin a popularity boost but led to international sanctions being imposed against Moscow.
Diplomats have emphasised that the issue of Crimea is not on the table at the summit, which the Kremlin has confirmed will include a one-on-one meeting between Mr Zelensky and Mr Putin.
Kiev has made clear its determination to never give up the peninsula, which the international community regards as part of Ukraine.
The goals of today'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.
Also key is agreeing a calendar for elections to be held in Donetsk and Lugansk, with the two regions enjoying a special status under Ukrainian law, 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," Mangott said.
Yesterday, Ukrainian Foreign Minister Vadym Prystaiko reiterated his country's key demands in a tweet: "A total and permanent ceasefire, our control over the borders of a unitary and indivisible state, the disarmament and dismantling of illegal armed groups, local elections in accordance with our legislation."
The Kremlin has sent signals that it is ready to work with Mr Zelensky, whom Mr Putin has described as "likeable" and "sincere".
But the Russian leader also will not want to return empty-handed and will be pushing for an easing of sanctions.
German Foreign Minister Heiko Maas told the Funke newspaper group ahead of today's summit that "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".
Mr Maas praised Mr 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".
"There remains the problem of trust between the parties," said the French presidential source, who asked not to be identified by name. "This needs to be created before we can move forward."
Today's summit is the first of its kind 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 for Donetsk and Lugansk, and the holding of local elections.
The summit is a hugely delicate event for everyone involved, but particularly for Mr Zelensky, who is under pressure not to cede ground to the Kremlin.