US STOCKS-Futures extend losses on bank write-down fears

(Updates with futures extending losses)

NEW YORK, Jan 23 (Reuters) - U.S. stock index futures fell further on Wednesday as fears of more write-downs at banks worsened a mood already soured by worries about a U.S. recession and a weak profit outlook from Apple Inc (AAPL.O).

S&P 500 futures SPc1 were down 35.70 points, below fair value, a mathematical formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract.

Dow Jones industrial average futures DJc1 dropped 251 points. Nasdaq 100 NDc1 futures slid 65.50 points. (Reporting by Kristina Cooke; Editing by Kenneth Barry)