The decision comes a day after Prime Minister Brian Cowen announced he would not lead his Fianna Fail party after elections, sparking a race to succeed him.

On Thursday, Cowen called for new elections March 11, but the defection of the Greens from the governing coalition will probably push a vote up even sooner. Opposition parties say the election should take place next month.

He is trying to push through measures to cut Ireland's deficit, which runs into the billions of dollars after the government bailed out its banks during the financial crisis.

The austerity measures and appeal for international financial aid have made Cowen and his government the focus of voter anger.

The Greens said on Sunday that they would support the austerity package when it comes up for a vote in parliament, despite pulling out of the government.

Opposition parties hope the package will be pushed through the Dail, Ireland's parliament, this week, though Cowen said on Sunday he saw that possibility as extremely unlikely.

A new leader will be elected to replace Cowen at a special party meeting on Wednesday afternoon. At least four senior Fianna Fail members have signaled that they intend to stand for the leadership post.

They include Finance Minister Brian Lenihan and Micheal Martin, who resigned last week as foreign affairs minister.