French Foreign Minister Jean-Yves Le Drian said there was a "window of opportunity" for resolving the Ukraine conflict after a landmark prisoner exchange on Saturday, but that it was too soon to talk of lifting sanctions on Russia.

Le Drian and French Defence Minister Florence Parly were in Moscow for talks under the so-called "2+2" format that been suspended since Russia's 2014 annexation of Crimea from Ukraine.

French President Emmanuel Macron has launched a diplomatic push for a detente in Europe's relations with Russia.

"The time has come, the time is right, to work towards reducing distrust," Le Drian told a press conference of the four ministers after the talks.

"We have come to suggest... a new agenda of trust and security."

He said the prisoner exchange -- which saw 35 detainees handed over on each side -- had created goodwill that needed to be reinforced.

"It is not yet the deadline for lifting sanctions. It's a new state of mind, which we have not seen for several years," Le Drian said.

Lavrov said progress on rebuilding ties with Europe was "possible and necessary".

- Prisoner swap 'a good sign' -

He welcomed recent statements by Ukrainian President Volodymyr Zelensky as "very, very positive" and described the prisoner exchange as "a good sign" for future progress.

Ties between Russia and Europe have been deeply strained since 2014, when the European Union and United States imposed sanctions over the annexation of Crimea and Russia's support for separatists in eastern Ukraine.

Macron embarked on his bid to bring Russia in from the cold this summer, hosting President Vladimir Putin in southern France last month and renewing high-level diplomatic contacts.

The two men spoke by phone on Sunday, hailing the prisoner exchange as a step forward in peace efforts.

Attempts to resolve the Ukraine crisis have revived since the election in April of comedian-turned-president Zelensky, who has made ending the conflict his main priority.

Macron announced a summit under the so-called "Normandy format" of France, Germany, Russia and Ukraine in his talks with Putin, but a date has not yet been set.

The focus of the summit will be reviving the Minsk accords, which Germany and France helped to negotiate but failed to stop the fighting in eastern Ukraine, where more than 13,000 have been killed.

Analysts said Macron is looking to take the lead on Russia in Europe. As head of the G7 and Council of Europe, and with Germany and Britain focused on internal politics, the French president sees an opportunity.

"Emmanuel Macron is telling himself that if there's a chance of doing something on Ukraine, it's now," said Florent Parmentier, a researcher at Sciences Po university in Paris.

"It won't be easy but it's not a rash move," he added, pointing to France's "real diplomatic advance" by promoting Russia's return to the Council of Europe, the continent's foremost human rights body, last June.

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