U.S. stock index futures were little changed on Thursday after posting their biggest one-day gains in about six weeks and as investors readied for data on jobless claims and retail sales for clues about the direction of the economy.

The S&P 500 index rose more than 3 percent on Wednesday as a strong outlook from State Street Corp lifted optimism ahead of the upcoming earnings season. A strong June sales tally from retailers could bolster the gains.

Top U.S. warehouse club operator Costco Wholesale Corp's June same-store sales rose 4 percent but just missed Wall Street's expectations because of a holiday shift in the period.

All bets are off until we start seeing how June (comparable) store sales came in, said Craig Peckham, equity trading strategist at Jefferies & Co in New York. There is a lot of concern about just how well the U.S. consumer held up.

Target Corp , Kohl's Corp and JC Penney Co are due to report monthly sales on Thursday, and an overall rise in June would mark the 10th consecutive month of rising sales after a year of declines during the recession.

S&P 500 futures fell 1.6 points but were slightly 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 fell 8 points, and Nasdaq 100 futures lost 2.5 points.

The S&P 500 has fallen nearly 13 percent from a peak in April, with investors concerned about a slowdown in economic growth in the United States, Europe and China.

Striking an optimistic note on the economy, the International Monetary Fund upgraded its 2010 global growth forecast, citing robust expansion in Asia and renewed U.S. private demand, but warned the euro area's debt crisis posed a big risk to recovery.

U.S. economic data on Thursday includes new jobless claims, due at 8.30 a.m. ET, which are expected to have slipped to 460,000 in the latest week. In the previous period, they rose to 472,000 from 457,000, undermining confidence in the labor market.

The FTSEurofirst 300 index of leading European shares was up 0.6 percent, extending a rally into a third day, with banks among major gainers. Japan's Nikkei average closed up 2.8 percent in a follow-through to U.S. gains on Wednesday.

Details of stress tests for Europe's banks have started to emerge, lifting confidence in the battered sector. A news conference at the European Central Bank on Thursday is expected to focus on the tests, giving investors more clarity.

Crude prices rose to $74.56 a barrel, reinforcing overnight gains after a report showed U.S. crude inventories plunged last week.

(Reporting by Edward Krudy; Editing by Padraic Cassidy)