Lagarde called a news conference for 5:45 a.m. ET on May 24, at which a Finance Ministry official said she would make an important announcement, but declined to comment further.

"I understand that what Mrs Lagarde is going to announce is her candidacy. It's all clear now on the European side, we've reached a consensus," a diplomatic source said.

A second source also said EU countries had agreed to back her to replace Dominique Strauss-Kahn, who quit last week over sexual assault charges.

"Some countries are less positive than others but, as there are no alternative candidacies, Mrs Lagarde's is obvious," the first source said.