Russia’s economy is under growing strain as its invasion of Ukraine drags on and Western sanctions are undermining President Vladimir Putin’s ability to sustain his war, a leading European economist said after briefing finance ministers on Tuesday.

"Massive" sanctions European leaders threatened to impose on Russia if Vladimir Putin does not agree to a ceasefire in Ukraine face formidable political obstacles and would need U.S. support to succeed,

The new round of negotiations comes amid a long history of delaying tactics by the Russian side as the fighting in Ukraine grinds on.