IMF chief Christine Lagarde has stressed Greece's huge debt pile needs restructuring and said the organisation remains "fully engaged" with the cash-strapped country.
"Greece is in a situation of acute crisis, which needs to be addressed seriously and promptly," she said during a speech at the Brookings Institution think-tank in Washington.
Earlier today Greek Prime Minister Alexis Tsipras made a formal request for a three-year bailout from the Eurozone's rescue fund and promised to implement tax and pension reforms as early as next week.
Last night Brussels ramped up the pressure on Greece ordering it to submit a completed reform plan by midnight on Thursday, while European Council president Donald Tusk said Athens has until Sunday to reach an "ultimate agreement".
An emergency summit is due to be held on Sunday between all the 28 members of the European Union, not just those in the Eurozone.