Peace talks between Ukraine's leaders and Kremlin-backed rebels could take place Sunday or Monday in the Belarussian capital Minsk in the presence of Russian and OSCE envoys, French President Francois Hollande said.

These talks will "happen on Sunday or Monday," Hollande said after an EU summit on Thursday, referring to the peace talks that will take place between the rebels and the Ukrainian government delegates in Minsk.

New EU president Donald Tusk said Thursday the bloc needs a strategy on Russia lasting years, not just weeks or months, to cope with the problems raised by its intervention in Ukraine.

"We need a long perspective strategy... plans for years. We need to be realistic, we have to treat this as a long-term game," Tusk said after chairing his first European Union leaders summit, which reviewed relations with Russia.

The irony is striking: just as the United States prepares to double down on sanctions against Russia, it has admitted that 50 years of sanctions against Cuba have been a failure.

"We will end an outdated approach that for decades has failed to advance our interests," said President Barack Obama on Wednesday as he drew the curtain on what one expert calls the "most drawn-out foreign policy mistake in U.S. history".

EU foreign policy chief Federica Mogherini on Thursday urged Russian President Vladimir Putin to make a "radical change" in attitude to end the crisis sparked by Moscow's intervention in Ukraine.

"The fact that Russia is in a difficult situation from a financial point of view is not good news, Mogherini told reporters, referring to the collapse of the Russian ruble, partly due to western sanctions.

President Vladimir Putin vowed Thursday that Russia would rapidly recover from its financial crisis and said his grip on power was firm, even as new Western sanctions and a run on the ruble pile on the pressure.

The Russian strongman, who is locked in a confrontation with the West, showed no willingness to change tack on Ukraine and dismissed the possibility of the country's elite turning against him.

Recent close shaves between Russian fighters and civilian aircraft highlight the dangers of the cat-and-mouse game being played out between Moscow and the West in European skies amid the crisis in Ukraine, analysts say.

In the latest incident, Sweden said Friday that a Russian military jet nearly collided with a passenger plane south of Malmoe shortly after take-off from Copenhagen International Airport.

Some 400 Russian sailors are returning home, French shipbuilder DCNS said Wednesday, as Paris weighs whether to deliver the Mistral-class warship to Russia amid the Ukraine crisis.

New internationally mediated peace talks between Ukraine, Russian-backed rebels and Russia itself could start Sunday in Minsk, Ukrainian President Petro Poroshenko said Wednesday.

"We agreed for the contact group to hold a video conference on Thursday and Friday," he said, referring to representatives from Kiev, Moscow, the rebels controlling parts of eastern Ukraine, and the OSCE European security body.

Russia's finance ministry is selling its foreign currency to support the ruble, a spokeswoman told AFP on Wednesday.

"The finance ministry considers the ruble extremely undervalued and is starting to sell its left-over currency on the market," spokeswoman Svetlana Nikitina said. She did not give details of the amount.

Russia's President Vladimir Putin and his French, German and Ukrainian counterparts agreed in a phonecall early Wednesday that they wanted talks between Kiev, Moscow and rebels controlling parts of eastern Ukraine to resume as soon as possible.

The telephone conversation came after the White House confirmed that U.S. President Barack Obama will sign into law fresh sanctions against Russia.