EU ministers discuss standby plans for Greece

Goldman Sachs economist Erik Nielsen said Greece would need to raise another 8-10 billion euros on markets before mid-May and that this could be the trigger point if the refinancing proved too stressful.

"If this is not feasible at an acceptable cost, then help will be provided," he said.

Dutch Finance Minister Jan Kees De Jager said any help would be tied to tough conditions of the kind that the International Monetary Fund applies when rescuing countries in trouble.

European Central Bank Executive Board member Lorenzo Bini Smaghi said "constructive ambiguity" could be useful to put pressure on countries or institutions to take necessary steps.

Writing in the Financial Times, he said authorities should be ready for a bailout as a last resort to prevent worse problems developing.

(With reporting by Jan Strupczewski and John O'Donnell; Writing by Brian Love; editing by Timothy Heritage and Dale Hudson)