Greece stands on the brink of a make-or-break general election that could sweep the anti-austerity Syriza party to power and set the country on a collision course with its international creditors.

Syriza wants to renegotiate Greece's massive 318 billion euro ($476 billion NZD) debt and put an end to years of wage cuts and public spending reductions linked to an international bailout.

The possibility of Alexis Tsipras' left-wing party winning Sunday's vote has sparked fears that Greece could fail to keep up its debt repayments and leave the euro. Syriza have a lead of at least four points over the incumbent conservative New Democracy party of Prime Minister Antonis Samaras, according to opinion polls.

In his final appeal to voters on Friday, Tsipras pledged to restore "dignity" to Greece. Samaras told his party's supporters in his closing rally that it would be crazy to elect Syriza just when the fiscal reforms he has supported could be about to pay off.

"Syriza will turn all of Europe against Greece.... They don't understand Europe, they don't believe in Europe," he said.

Greece has endured deep budget cuts tied to its 240 billion euro bailout from the so-called troika -- the European Union, International Monetary Fund (IMF) and European Central Bank (ECB).

Unemployment is around 25% and the economy has shrunk by a quarter since the start of the eurozone crisis.

Tsipras has said he wants to work out a solution on the debt with the ECB by July, and has promised to cut the amount by half.

A Syriza official told AFP the party was heading for victory and was confident of forming a coalition government if necessary.

"Polls show we are five to 10 points ahead of New Democracy. What remains to be seen is whether we will have a clear majority," the official said.

Samaras told reporters that up to 14% of voters remained undecided and predicted they would choose the "stability" he represented.

A victory for Syriza could pave the way for other anti-austerity parties to break through in Europe. The leader of Spain's radical Podemos movement, Pablo Iglesias, appeared with Tsipras at an Athens rally this week.

German Chancellor Angela Merkel on Friday appealed to Greece to stay in the eurozone.

"At the heart of our principles lies solidarity. I want Greece, despite the difficulties, to remain part of our story," she said.