"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,

A leading economist has been telling EU finance ministers that Russia’s economy is under growing strain as its invasion of Ukraine drags on.

"We are waiting for (Russian President Vladimir) Putin's agreement and we agree that if there is no real progress this week, we want to work together at European level for a significant tightening of sanctions," Merz said at a news conference with his Greek counterpart.