By JOE GOULD & CORKY SIEMASZKO
DAILY NEWS STAFF WRITERS

It was a Maalox Monday on Wall Street as stocks plunged 500 points in early trading, stoking fears the U.S. economy is on the brink of a recession - if not already in one.

Three days after the House approved a historic $700 billion bailout aimed at saving troubled U.S. banks and easing a credit crunch, there was little sign the agreement was allaying fears of a massive financial meltdown.

The Dow fell below 10,000 for the first time since October 2004 - stunning the trading floor into silence.

"There was a bunch of brokers standing around looking up at the board," said James, a 27-year-old trader who declined to give his last name.

"As soon it traded through 10,000, there was a moment of silence. You heard a whisper, a buzz, and then everyone was quiet. There are people definitely stressed in there."

The tumble appears to have been sparked by the realization that President Bush's "rescue" plan was not going to unfreeze credit markets right away - or make it easier for banks to get their hands on cash.

Meanwhile, a survey by the influential National Association for Business Economics (NABE) found that 69% of economists think the economy has started or will enter a recession this year - and that it won't get better until next year.

"The general view is ... that this recession will be longer than the last two - lasting roughly one year," the survey concluded.

The silver lining? It will be "relatively mild."

The 2001 recession started in March and ended in November. The one before that began in July 1990 and ended in March 1991.

Wall Street stocks began tumbling after governments across Europe rushed to prop up their own failing banks.

The German government agreed on a $68 billion bailout for commercial-property lender Hypo Real Estate Holding AG, while France's BNP Paribas agreed to acquire a 75% stake in Fortis's Belgium bank after a government rescue failed.

Germany, Ireland and Greece also said they would guarantee bank deposits.

In Iceland, where the currency went into freefall last week, there were reports of food hoarding after a supermarket spokesman said there wasn't enough foreign currency to import more food.