European leaders gave themselves until June to finalize an increase in their temporary bailout facility at a summit, failing to deliver the broad package they had promised to resolve their debt crisis.
Concern about Portugal, whose premier quit after austerity measures aimed at avoiding a bailout were thrown out by its parliament, dominated the meeting even if leaders chose not to discuss it openly.
The heads of government also extended the schedule for paying into a permanent rescue fund to be set up from mid-2013, giving themselves five years to provide capital of 80 billion euros, rather than doing it over a shorter period in bigger installments.
That was a concession to German Chancellor Angela Merkel, who had balked at the previous funding plan for the European Stability Mechanism (ESM) because it gave her less room to cut taxes before the next federal election in 2013.
European officials have said the fund will have a triple-A rating despite the longer funding timetable.
Having said for weeks that they would agree a comprehensive package to tackle the euro zone debt crisis at the two-day summit, the leaders were unable to finalize key decisions because of political hurdles in some of its 27-member states.
Although they agreed in principle earlier this month to boost the lending capacity of their temporary safety net -- the European Financial Stability Facility (EFSF) -- to 440 billion euros from roughly 250 billion, they had to push this back until mid-year because of looming elections in Finland.
Any agreement on debt relief for Ireland has also been delayed pending the results of bank stress tests next week which could show a sharp rise in losses at the country's stricken financial institutions.
Reflecting the threat investors see from Portugal, yields on its 10-year benchmark bonds rose above 8 percent on Friday, a rate that is considered unsustainable in the long term, making a bailout more likely.
The euro itself was little moved.
President Anibal Cavaco Silva will meet the leaders of Portugal's political parties on Friday to decide whether to call a snap election.
Prime Minister Jose Socrates is the second euro zone leader to fall victim to the rolling sovereign debt crisis after Ireland's prime minister was voted out of office last month.
Attending the summit, Socrates made clear his continued opposition to Portugal asking for a bailout, and said that whatever Portuguese government comes to power after new elections, it would stand by its deficit-cutting commitments.
If Portugal's president calls for new elections, by law they cannot be held for a further two months. Any decision on whether to seek a bailout may only therefore be taken in May. Portuguese voters are opposed to any EU/IMF assistance.
Luxembourg Prime Minister Jean-Claude Juncker said he did not expect Portugal to seek assistance from the EU rescue fund any time soon.
The situation in Portugal is very complicated. But nothing suggests that Portugal will put in a request any time soon, he told Deutschlandfunk radio.
The fall of the government prompted both Standard & Poor's and Fitch to cut Portugal's credit rating by two notches.
The Portuguese upheaval underscored the wealth of political obstacles the single currency bloc faces in trying to solve a debt crisis that has deepened over the past year.
As well as Portugal there are concerns about Ireland, particularly its heavily indebted banks. Ireland has already received an 85 billion euro bailout package, but there are concerns it may need even more to recapitalise troubled lenders.
Senior euro zone officials said Portugal was likely to need 60-80 billion euros in assistance from the EU rescue fund and the International Monetary Fund.
Lisbon needs to refinance about 4.5 billion euros of debt in April and a similar amount in June, which may prove a trigger for finally making the request for aid. One problem is that any bailout request would have to be approved by parliament and the majority is opposed to asking for help.
With Portugal widely expected to seek assistance, attention could soon shift to Spain, which has gradually won back the confidence of investors in recent months by unveiling reforms of the labor market and pension system, as well as a plan for shoring up its ailing savings banks.
In a sign that contagion worries remain, sources told Reuters in Washington that the head of the International Monetary Fund (IMF) would seek approval from member countries next week to activate a $580 billion crisis fund.
The biggest worry is the high risk of contagion from Portugal and general global uncertainty will trigger a new wave of borrowing from the fund, one source said, noting that Spain held one-third of Portugal's public debt.
(Reporting by Marc Angrand, Rex Merrifield, Jan Strupczewski)
(Writing by Noah Barkin, Luke Baker and Paul Taylor, editing by Mike Peacock)