New York - Stock index futures tumbled on Sunday, pointing to a sharply lower open on Monday amid widespread uncertainty about the health of U.S. financial sector with the fate of Lehman Brothers still unclear.

The ruptured U.S. financial system was facing an unprecedented shake-up on Sunday that could lead to the failure of Lehman Brothers (LEH.N), the takeover of Merrill Lynch & Co Inc. (MER.N) and huge asset sales by American International Group (AIG.N).



S&P 500 futures fell 38 points and the Dow Jones industrial average futures sank 307 points while Nasdaq 100 futures slid 45 points.