Talks due on Republic of Ireland election date
Irish finance minister Brian Lenihan is due to hold talks later with opposition parties to see if the country's general election can be held before 11 March.
On Sunday, the Republic's Green Party pulled out of the ruling coalition with Fianna Fail.
The Greens' announcement wiped out the coalition's two-seat majority.
On Saturday Brian Cowen quit as leader of Fianna Fail party but said he would stay on as prime minister. Opponents said this was "farcical".
Mr Lenihan is also a candidate to replace Mr Cowen as Fianna Fail leader. Nominations for that contest close at lunchtime.
The Green Party said it would try to help Mr Cowen push through a crucial bill aimed at restoring stability to the economy.
Green Party senator Mark Deary said if the bill is passed this week, a February election is "inevitable".
"If the finance bill can be concluded by the end of this week, a three-week campaign would bring us to 18 February, a four-week campaign to 25 February.
"It's the Taoiseach's (prime minister's) prerogative as to which option to choose, but certainly a February election is now on the cards."
Fianna Fail had urged the Greens to stay in government to ensure the financial bill - which is needed as part of Ireland's international bail-out package - was passed before the election.
Ireland was forced to accept the 85bn euro ($113bn; £72bn) EU and IMF bail-out in November last year.
When asked whether he would now resign immediately, Mr Cowen said getting the finance bill through was the main issue.'Persistent doubts'
The Green Party will join the opposition benches immediately.
But it said it hoped Fianna Fail would fast-track the finance legislation so it could be approved speedily.
After Brian Cowen's resignation, Fianna Fail is now a party without a leader and a coalition partner, and pressure is growing for a general election earlier than the 11 March date announced last week.
Mr Gormley's statement makes it a virtual certainty that the people of the Republic will go to the polls sometime in February.
But the fog of uncertainty remains.
That's because we still don't know whether the finance bill can be passed and, if so, when. Nor do we have a date for a general election, although it will almost certainly be sooner rather than later.
The opposition parties have threatened votes of no confidence in both the Irish prime minister, or taoiseach, and his government this week.
If the votes go ahead it is unlikely the minority Fianna Fail government can win.
Green Party leader John Gormley, speaking after a meeting in a Dublin hotel, said: "For a very long time we have stood back in the hope that Fianna Fail could resolve persistent doubts about their party leadership.
"A definitive resolution of this has not yet been possible and our patience has reached an end. Because of these continuing doubts, the lack of communication and the breakdown in trust, we have decided that we can no longer continue in government.
"We will remain true to our promise to support the finance bill from the opposition benches."
After the Greens' announcement, Mr Cowen said: "The important thing now is to have an orderly completion of the finance bill in the interests of the country and then obviously we move to a dissolution of the [parliament] and a general election."
The loss of two Green Party cabinet ministers means Mr Cowen now only has seven of 15, the minimum constitutionally allowed.
The focus next week will fall on the finance bill and a no-confidence motion put forward by the opposition for Tuesday.
If Mr Cowen lost the motion he would be obliged to resign and call an election within four weeks.
Correspondents say he might try to persuade the opposition to hold off on that vote to allow for debate and passage of the finance bill, which is designed to cut the government's deficit.
The Greens want all-party talks on Monday to rush the bill through as soon as possible.
But the BBC's Ireland correspondent Mark Simpson says its passage is not assured, given the country's political system is in a state of chaos and filled with bitterness.
Mr Cowen's assertion on Sunday that it is "not possible to deal with it in a week" is unlikely to please the opposition.Bungled reshuffle
Mr Cowen has been under increasing pressure over his handling of the economy and party disputes.
The criticism intensified this month following revelations he played golf with the former chairman of Anglo Irish Bank, Sean FitzPatrick, months before the bank was nationalised to prevent it from collapse. Mr Cowen has denied any wrongdoing.
Last Tuesday, Mr Cowen won a vote of confidence in his leadership of Fianna Fail. Minister for Foreign Affairs, Micheal Martin, who had opposed Mr Cowen, resigned.
However on Thursday, Mr Cowen bungled a planned government reshuffle. The Greens were angered and blocked the reshuffle. Mr Cowen then called the general election.
His decision on Saturday to resign as Fianna Fail leader while remaining PM was met with an angry response by the opposition Fine Gael, Labour and Sinn Fein parties.
Labour leader Eamon Gilmore said it was "simply not tenable" for Mr Cowen to remain PM.