By Reed Stevenson and Philip Blenkinsop

Trichet, who as ECB head is responsible for safeguarding financial stability in the euro zone, joined Belgian Prime Minister Yves Leterme in Brussels in a frantic drive to secure the future of the cross-border bank and insurance group.

BNP Paribas and ING Group both declined comment on reports they could buy all or part of Fortis, one of Europe's top 20 banks, or split off Dutch bank ABN AMRO, which Fortis bought a year ago, precipitating its troubles.

The presence of the ECB chief -- unprecedented in a commercial bank rescue -- underlined the seriousness of concern for the integrity of the euro zone's financial system.

After Fortis' board held an emergency meeting, new CEO Filip Dierckx joined the Belgian and Dutch ministers and central bankers meeting with Trichet nearby at the Belgian parliament.

A document Dierckx carried into the meeting, photographed by Reuters, listed a range of options including "Fortis sells its stake in ABN AMRO for x billion euros to xx" and "governments of Belgium and Luxembourg to invest xx billion euros in Fortis."

The draft press release said Fortis Chairman Maurice Lippens, blamed by shareholders for poor communication over the bank's troubles, would resign.

Fortis' portfolio of structured credit would be written down by an unspecified number of billions of euros, and the Belgian and Luxembourg governments would provide a "liquidity back-stop," it said.

Luxembourg Budget and Treasury Minister Luc Frieden said the Dutch, Luxembourg and Belgian governments would all buy stakes in the cross-border bank unless a foreign bank buyer emerged.

"Either one foreign bank takes over the entire group (or) if this doesn't work out because it is difficult over a weekend, the second option is to make sure that for the Luxembourg bank (Fortis Banque Luxembourg) the Luxembourg state will play an important role. The Belgian government would do the same in Belgium, the Dutch government in the Netherlands," he told RTL television.

Dutch newspaper Het Financieele Dagblad said ING had withdrawn from the talks.

ABN PURCHASE BLAMED

The problems at Fortis, whose shares dropped by a third last week on investor concerns about its liquidity and funding, stem from last year's 70 billion euro purchase of ABN with partners Royal Bank of Scotland and Spain's Santander.

A key issue in the future of Fortis was whether the governments or the ECB would provide financial guarantees, a source familiar with the situation said.

Belgian Social Affairs and Health Minister Laurette Onkelinx said all elements of a solution for Fortis were on the table and the Belgian Prime Minister would make a statement later.

Officials from central banks, supervisors and government treasury departments were also converging in Amsterdam on Sunday for a long-scheduled meeting of the Financial Stability Forum (FSF) chaired by Bank of Italy Chairman Mario Draghi, with a news briefing brought forward to Monday from Tuesday.

Fortis, which employs 85,000 people worldwide, has been weighed down by its 24 billion euro outlay for ABN in a market that is neither conducive to more capital increases nor willing to pay for the assets it wants to sell.

Its shares plummeted more than 20 percent to 15-year lows on Friday despite a statement that its position was strong and a pledge to expand asset sales to as much as 10 billion euros to raise cash.

The group's market capitalization slumped from 50 billion euros after the ABN purchase to just 12 billion euros on Friday. By comparison, BNP Paribas was worth about 62 billion euros at Friday's market close.

The stakes are high in Belgium, where Fortis is the biggest private sector employer and more than 1.5 million households, roughly half the country, bank with the group.

Marianne Thyssen, chairwoman of Prime Minister Leterme's Christian Democrats, told Belgian television it was important the public should know their savings were safe.

"The government is ready to guarantee the full 100 percent."

Fortis named Dierckx as chief executive on Friday evening, hastily replacing caretaker Herman Verwilst.

In London, regulators were in talks on the future of troubled lender Bradford & Bingley, raising the prospect that a second British bank could be nationalized.

Financial players around the world were hoping that U.S. lawmakers would finally sign off on a deal to create a $700 billion government fund to buy bad debt from ailing banks in a bid to stem a credit crisis threatening the global economy.

(Additional reporting by Antonia Van De Velde, Yves Herman, Marcin Grajewski in Brussels, Michele Sinner in Luxembourg, Steve Slater in London; Writing by Paul Taylor and Reed Stevenson; Editing by Paul Bolding and Alexander Smith)