It may take the International Monetary Fund until the second quarter to decide on whether to take part in a third bailout for Greece, Reuters cited the lender's chief Christine Lagarde as telling a German newspaper on Friday.

She added in remarks to Sueddeutsche Zeitung that the question of debt sustainability and progress on Greek pension reforms would be key to any participation.

"It is clear that pension reform is the trigger that will prove that Greece's economic position is improving," she was quoted as saying.