By Reed Stevenson and Philip Blenkinsop

Financial authorities in Belgium and the Netherlands were preparing to provide reassurances on the integrity of the Benelux financial system later on Sunday, after holding intense discussions late into Saturday evening, a source familiar with the situation said.

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.

The FSF said it was bringing forward a briefing by Draghi, a member of the European Central Bank's Governing Council, to Monday instead of Tuesday as originally scheduled. It did not say why.

Fortis's problems stem from its purchase last year of ABN AMRO with partners Royal Bank of Scotland and Spain's Santander

in a 70 billion euro ($102 billion) deal just as the credit crisis struck, slashing the value of banking assets.

"The sale of ABN AMRO is being considered," Dutch financial daily Financieele Dagblad reported on its Web site, citing an unnamed source.

Fortis has been weighed down by its 24 billion euro outlay in a market that is neither conducive to more of its capital increases nor willing to pay handsomely for the assets it wants to sell.

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.

POTENTIAL BUYERS?

BNP Paribas is a potentially interested buyer for all of Fortis or just ABN, while Dutch rivals ING or Rabobank may be eyeing Fortis's private banking business, the Dutch newspaper added, citing to unnamed sources.

Belgian daily De Standaard said on its website that BNP and ING were favorites to buy all or part of Fortis, with investment bankers already advising.

The CBFA and the central bank were examining initiatives to restore confidence in Fortis, with a decision and likely announcement in the late afternoon or evening, a CBFA spokesman said. Dutch counterparts were also working to resolve the Fortis crisis.

The Dutch central bank (DNB) governor Nout Wellink, a European Central Bank governing council member, canceled a weekend trip to Chicago to return to the Netherlands.

As its shares plummeted more than 20 percent to 15-year lows on Friday, Fortis called an emergency news conference to say its position was strong and that it would expand asset sales to as much as 10 billion euros ($14.6 billion) to raise cash.

Core members of Belgian Prime Minister Yves Leterme's cabinet met for two hours late on Saturday for a briefing with Belgium's financial regulator, the Banking, Finance and Insurance Commission (CBFA) and the central bank.

Financial authorities have contacted a number of institutions, a source familiar with the situation told Reuters on Saturday, although there was no preferred solution.

The stakes are high in Belgium, where Fortis is the biggest private sector employer and where over 1.5 million households, roughly half the country, bank with the group. For what's at stake for Belgium, see.

After a fifth straight day of share declines, Fortis also on Friday named a new chief executive, nominating banking chief Filip Dierckx, 52, to replace interim CEO Herman Verwilst.

Financial players around the world were hoping that U.S. lawmakers would sign off on a deal on Sunday 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.

(Reporting by Reed Stevenson and Philip Blenkinsop; Editing by Paul Bolding)