Hypo said an original euro35 billion ($48 billion) rescue plan fell apart after private lenders withdrew support, a key element to the proposal that had already been approved by the EU.
The deal was on top of the guarantees of private accounts. German Finance Ministry spokesman Torsten Albig said the unlimited guarantee covered some 568 billion euros ($785 billion) in savings and checking accounts as well as time deposits, or CDs.
At the same time, Belgian Prime Minister Yves Leterme said that France's BNP Paribas SA had committed to taking a 75-percent stake in Fortis NV.
Leterme said the Belgian and Luxembourg governments would, in turn, take a blocking minority share in BNP Paribas.
The deal came after two days of closed-door talks between the Paris-based bank, Fortis and government authorities in an effort to restore confidence in the company before markets open Monday.
In Iceland - particularly hard-hit by the credit crunch - government officials and banking chiefs were discussing a possible rescue plan for the country's overstretched commercial banks. British treasury chief Alistair Darling said he was ready to take "pretty big steps that we wouldn't take in ordinary times" to help the country weather the credit crunch.
In the past year the government has nationalized struggling mortgage lenders Northern Rock and Bradford & Bingley.
"The European banking industry is feeling the wind of default blowing from the other side of the Atlantic," said Axel Pierron, senior vice president at Celent, a Boston, Massachusetts-based financial research and consulting firm.
The erosion has also injured overall confidence and caused concern among investors, politicians and the European public. The leaders of Germany, France, Britain and Italy met Saturday to discuss the meltdown that has leapfrogged across the Atlantic from the U.S. to Europe, but shied away from action on the scale of the massive $700 billion bailout passed by the U.S. Congress on Friday and later signed into law by President Bush.
Their failure to agree to an EU-wide plan showcased the divisions in Europe on how to deal with the crisis.
France had suggested a multibillion-euro (multibillion-dollar) EU-wide government bailout plan, but backed off after Germany said banks must find their own way out.
French President Nicolas Sarkozy's top adviser, Claude Gueant, insisted that a "common European plan" had come out of the summit.
"What is certain and what the citizens of France and Europe must know is that their (banking) establishments won't be left in difficulty," he told Europe-1 radio on Sunday.
Icelandic banks expanded rapidly after deregulation of the domestic financial market in the 1990s and now have combined foreign liabilities in excess of 100 billion euros ($138 billion) - dwarfing the tiny country's gross domestic product of 14 billion euros ($19 billion euros).
The government last week took over Iceland's third-largest bank, Glitnir, a decision that prompted major credit ratings agencies to downgrade both Iceland's four major banks and its government credit rating.
Looming large was a growing sense that the Federal Reserve and Europe's major central banks - which have been flooding euros and dollars to banks that have grown increasingly unwilling to lend money even to themselves - were ready to institute emergency cuts to their benchmark interest rates this week.
None of the banks, including the European Central Bank and Bank of England, have commented on potential rate hikes or cuts. But analysts believe the Bank of England, which meets this Thursday, will likely lower its rate below 5 percent. The ECB left its rate unchanged at 4.25 percent on Thursday, but opened the door to a rate cut.
Robert Brusca, chief economist at the New York-based Fact and Opinion Economics, said that the ECB does issue such a cut it would a be a sign "that they're really, really scared."
Associated Press writers Angela Doland in Paris, Patrick McGroarty in Berlin and Jill Lawless in London contributed to this report.