|Greece's debt problem has sparked streets protests that have sometimes turned violent [Reuters]
Greece's two main unions, representing about half of the four million-strong workforce, have promised one of the biggest strikes, intensifying resistance to more austerity cuts.
The unions lashed out at the government on Monday with protests, strikes and ministry building sit-ins, as parliament prepared to vote on a sweeping package of austerity measures demanded by international lenders.
A 48-hour general strike is expected to begin on Wednesday and Thursday that will ground flights for two days, cripple public and many private services and even leave bakeries without workers.
The strikes have halted ferries to the Greek islands and left rotting trash piling up on the streets of Athens for a 16th straight day.
Tax collectors and customs officers walked off the job and protesting civil servants occupied the finance and labour ministry buildings in the Greek capital, Athens.
The government was considering using the army to help clear the trash, but was to decide on emergency plans later in the day, an official with knowledge of the contingency plans told The Associated Press.
"The government is destroying its central administration and cutting away the safety net for our citizens, while dramatic cuts in pay are driving workers into poverty and depravation," the civil servants' union ADEDY said.
"The latest measures are the deathblow for our income."
George Papandreou, the prime minister trailing badly in opinion polls, has defied the protests, pledging to push through a deeply unpopular package that includes tax rises, pay and pension cuts, job layoffs and changes to collective pay deals.
"It will demonstrate that we, by ourselves, are seeking to make major changes," he said at an emergency meeting with Karolos Papoulias, the president.
"It will mean we can go to the (debt) negotiations ... with our heads held high and with a stronger negotiating position."
Greece faces a key vote on new austerity measures on Thursday, while other eurozone countries are rushing to find a comprehensive solution to Europe's escalating debt crisis in time for a Sunday summit by European leaders.
Trapped in deep recession and strangled by a public debt equivalent to some 162 per cent of gross domestic product, Greece has been shut out of bond markets and would run out of money within weeks without international support.
Many economists believe Athens can no longer avoid defaulting on its debt, but in a newspaper interview on Sunday, Papandreou said a default would be a "catastrophe" for Greece.
Inspectors from the EU and the International Monetary Fund were in the capital Athens last week and have recommended releasing a vital 8bn euro aid tranche to enable the government to keep paying its bills past November.
That will only provide temporary relief, and they urged Papandreou's struggling Socialist government to push ahead with further belt-tightening, on top of what are already the deepest cuts in Greece's postwar history.