S&P 500 stock index futures briefly edged higher on Thursday after JPMorgan Chase reported earnings, but concerns over sovereign debt issues in Europe and U.S. budget talks meant gains were short lived.

* S&P 500 futures fell 0.7 point and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures rose 4 points, and Nasdaq 100 futures added 5.5 points.

(Editing by Kenneth Barry)