Half of all Greeks oppose pension reforms that Parliament is set to approve this week, but almost as many say the cuts are necessary, according to a newspaper poll published on Sunday.

A total of 19 per cent said the reforms would be "catastrophic" and another 29.6 per cent are against them, said the survey for the pro-government To Vima newspaper.

But 35.2 per cent of Greeks said they were "necessary even if unjust" and 14.2 per cent fully supported the reforms, which would reduce pensions and increase the retirement age to 65.

They are part of the austerity measures adopted by Greece's Socialist government in exchange for a three-year, €110-billion European Union-International Monetary Fund bailout package.

Prime Minister George Papandreaou said in an interview published in the left-leaning Eleftherotypia daily on Sunday that he was "confident" the measures would be adopted by Parliament on July 8.

He said that lawmakers were aware of their "responsibility to change the country".

Greek unions have called a general strike - their sixth this year - on the day of their vote.