"While the exchange has, in our view, alleviated near-term funding pressures, Greece's sovereign debt burden remains high," S&P warned as it raised the credit rating to CCC, with a stable outlook.

The rating firm warned that the recession and a May 6 general election were posing risks to fiscal adjustments needed to further cut Greece's debt.

"The ratings could be lowered if we believe that there is a likelihood of a distressed exchange on Greece's remaining stock of commercial debt," it said in a statement.

Fitch assigned Greece a speculative B-rating mid-March, becoming the first major rating agency to lift the country out of default territory after the debt swap cut Athens' debt mountain by about 100 billion euros, or close to a third.

(Reporting by Ingrid Melander. Editing by Jeremy Gaunt.)

• A Permanent Economic Emergency