Greece will need debt relief far beyond what eurozone partners have been prepared to consider due to the devastation of its economy and banks in the last two weeks, a confidential study by the International Monetary Fund seen by Reuters shows.

The updated debt sustainability analysis was sent to eurozone governments late on Monday, hours after Athens and its 18 partners agreed in principle to open negotiations on a third bailout program of up to 86 billion euros in return for tougher austerity measures and structural reforms.

"The dramatic deterioration in debt sustainability points to the need for debt relief on a scale that would need to go well beyond what has been under consideration to date -- and what has been proposed by the ESM," the IMF said, referring to the European Stability Mechanism bailout fund.

European countries would have to give Greece a 30-year grace period on servicing all its European debt, including new loans, and a very dramatic maturity extension, or else make explicit annual fiscal transfers to the Greek budget or accept "deep upfront haircuts" on their loans to Athens, the report said.

[Reuters]