U.S. stock index futures trimmed gains after a report showed sales at U.S. retailers unexpectedly fell in July from June.

* S&P 500 futures were up 5 points, or 0.5 percent, and above 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 61 points, or 0.65 percent, and Nasdaq 100 futures gained 9.75 points or 0.6 percent.

* Futures were up more than 1 percent in earlier trading after Wal-Mart Stores Inc reported better-than-expected quarterly results.

(Reporting by Angela Moon; Editing by Padraic Cassidy)