U.S. stock futures remained almost unchanged as a report depicted China's manufacturing expended less than previously expected, thus leading to concerns that the world's second-biggest economy might tumble. Contracts on the Standard & Poor's 500 Index with time to maturity in June slid 0.1% to 1,554.4, while futures on the Dow Jones Industrial Average also declined 0.1%, down 10 points, to 14,489 today.