Greece's conservative government has survived a no-confidence vote in parliament, fending off the prospect of snap elections.
Mr Karamanlis says the polls will be held "when they are due" - in 2008
The censure motion - which was brought by the Socialist opposition - was defeated in a 164-122 vote.
After the vote, Prime Minister Kostas Karamanlis vowed to press ahead with his reform programme which would require a constitutional amendment.
The Socialists have accused the government of being incompetent.
"We will continue our reforms in health, education and the economy, and nothing will stand in our way," Mr Karamanlis said after the vote, that followed three days of heated debates in parliament.
Mr Karamanlis said his New Democracy government was determined to complete its term, which ends in 2008.
"We have some way to go but we will succeed," the prime minister said, adding that the polls "will be held when they are due".
The Socialists submitted the motion on Friday, demanding early elections over what they said was the government's failure after three years in power.
Proposed reforms in education have triggered protests
"Enough is enough... you are not serious, you are dangerous for democracy," Socialist party chief George Papandreou told parliament.
The Socialists are now expected to walk out of the debate on constitutional revision, which Mr Karamanlis has described as the "flagship of reforms".
Proposed reforms in education triggered mass student street protests in Athens last month.