Greek Finance Minister Evangelos Venizelos has announced his resignation in order to head the Socialist party.
Venizelos was the only candidate for the leadership of the Pasok party in the March 18 selection, and he was expected officially to take over from his predecessor, former Prime Minister George Papandreou, on March 19.
The Pasok-led coalition government has not indicated who will be appointed finance minister to replace Venizelos.
The development comes just days after eurozone countries formally approved a second multibillion-euro bailout to help Greece avoid defaulting on its sovereign debt.
An early general election is expected in Greece in April or May, although no firm date has been set.
With AP and AFP reporting