NEW YORK (Reuters) - Stocks fell in volatile trading on Tuesday, with the S&P ending below 700 for the first time since October 1996 as persistent uncertainty about the amount of money needed to shore up the financial system overshadowed a hunt for bargains.
* Stocks swung to both sides of the break-even mark throughout the session with the S&P's ultimate break below the key psychological level of 700 adding to the gloom.
* Federal Reserve Chairman Ben Bernanke left the door open to whether banks will need more money when he said the size of a $700 billion bank-rescue package would depend on bank "stress tests" being conducted by regulators and the direction of the economy.
* The Dow Jones industrial average <.DJI> dropped 37.27 points, or 0.55 percent, to end unofficially at 6,726.02. The Standard & Poor's 500 Index <.SPX> fell 4.49 points, or 0.64 percent, to 696.33. The Nasdaq Composite Index <.IXIC> slipped 1.84 points, or 0.14 percent, to 1,321.01.
(Reporting by Charles Mikolajczak; Editing by Jan Paschal)
