Stock index futures trimmed gains slightly on Wednesday after data showed private employers unexpectedly cut 10,000 jobs in August.

Even so, futures remained sharply higher after China's manufacturing economy staged a moderate rebound in August after slowing for several months, while Australia's economy grew at its fastest pace in three years last quarter on a boost in household spending.

S&P 500 futures rose 11.5 points and were 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 climbed 86 points, and Nasdaq 100 futures gained 23.5 points.

(Reporting by Leah Schnurr; editing by Jeffrey Benkoe)