Greek lawmakers are debating a confidence vote called by the country's coalition government in a bid to bolster support among its backbenchers ahead of a presidential vote early next year.

The three-day debate is expected to end with a vote late Friday night after speeches by Conservative Prime Minister Antonis Samaras and the opposition leader.

Samaras is expected to win the vote and thereby allay fears of renewed political instability. He controls 155 of Parliament's 300 seats midway through his four-year term.

However, next year Samaras would need opposition support to avoid a stalemate and snap election in February when parliament elects the country's new president.

The anti-economic-bailout Syriza party is leading opinion polls by promising to renegotiate the tough terms of Greece's 240 billion euro ($302 billion) international bailouts.