Wall Street managed a moderate gain in an erratic session as investors sorted through a downbeat Federal Reserve assessment of the economy and were also disappointed by a plan to bail out troubled bond insurer Ambac Financial Group Inc.

The New York stock exchange plunged at the opening of trading today despite a last-minute interest rate cut by the US central bank.

Wall Street suffered one of its worst losses of 2007 today, leading a global stock market plunge as investors succumbed to months of worry about the mortgage and corporate lending markets.