Talks on forming a new Greek government appear to be deadlocked.
An announcement on who will lead the unity government had been expected on Wednesday.
However, the smallest party in the coalition negotiations has walked out, the BBC reports.
Talks are now due to resume on Thursday.
Earlier on Wednesday Prime Minister George Papandreou made a live television address to his country, saying he was resigning to make way for the new coalition government.
The unity government has only one task - to pass the European Union bailout package required to stave off bankruptcy.
In his speech, Mr Papandreou promised Greece would implement the package and do everything it can to stay in the eurozone.
However, he did not name his successor.