S&P 500 index futures fell on Tuesday, losing earlier gains, on continuing geopolitical concerns in the Middle East and worries over the nuclear crisis in Japan.

S&P 500 futures fell 1.6 points and were in line with 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 were up 1 point, and Nasdaq 100 futures added 1.5 points.

(Reporting by Angela Moon; editing by Jeffrey Benkoe)