(CNN) -- The aid package being negotiated to bail out Greece is worth 120 billion euros (about $160 billion) through 2012, according to Vassilis Papadimitriou, a spokesman for Greek Prime Minister George Papandreou.
But the International Monetary Fund and European Union are demanding further austerity measures as a price for the bailout, according to a top Greek labor union official.
Greece will be required to cut civil servants' salaries, freeze their pay increases, reduce their pension payments, change tax rates and increase the value-added tax consumers pay on purchases, according to Ilias Iliopoulos, the general secretary of the public sector union ADEDY.
The International Monetary Fund did not respond immediately to a CNN request for confirmation of the value of the package. Its head, Dominique Strauss-Kahn, said Wednesday the agency did not release information about deals in the works until they were done.
"Until we reach this point there is no precise information to give because the information doesn't exist," he said.
Greece's credit rating has been slashed twice in the past two weeks -- most recently being downgraded to "junk" -- raising fears for the euro currency used by 16 nations across Europe.
Markets worldwide tumbled when Standard & Poor's downgraded Greece earlier this week. It's the first European country to fall below investment grade.
The downgrade -- which makes it harder and more expensive for a country to borrow money -- was a major problem for Athens as it struggles to crawl out from beneath the country's massive debt.
The national debt of 300 billion euros ($394 billion) is bigger than the country's economy, and some estimates predict it will reach 120 percent of gross domestic product in 2010.
Germany is expected to contribute the lion's share of EU funding to bail out Greece. German Chancellor Angela Merkel said Wednesday her country will do what it can to help Greece out of its financial crisis, "but also Greece has to do its part."
She was meeting with Strauss-Kahn to hammer out specifics of the deal.
"Obviously what Greece has to do is a difficult thing, but I think they are committed to doing it," he said in an appearance with the German leader.
Merkel is being pulled in two directions -- toward bailing out Greece in order to stabilize the euro, and away from forking out cash because it is unpopular with German voters, with local elections coming up soon.
Former Greek Finance Minister George Alogoskoufis said Thursday that German taxpayers have nothing to worry about.
"German taxpayers are going to make money" when Greece repays the loans, he said on CNN's "Quest Means Business."
"Greece will never default," he added.
He said the country needed the aid package because it no longer had the options it used to have for raising funds.
"The markets have closed, we cannot rely on the markets as we have relied on the markets for so many years," he said.
Standard & Poor's slashed Spain's debt to a "AA" rating Wednesday, down from "AA+," as Merkel and Strauss-Kahn focused on Greece.
Spain's economy is among the largest in the European Union, significantly bigger than Greece's.
Greek civil servants and private sector workers are planning a 24-hour strike May 5 to protest government austerity measures, the unions announced Wednesday. Sporadic demonstrations have already taken place in several cities, with sometimes violent clashes between police and protesters angry about the coming changes.
Journalist Mary Retiniotis contributed to this report.