NEW YORK, March 20 (Reuters) - Renewed concerns about China's economic growth weighed on global stocks on Tuesday, giving a boost to safe-haven assets such as U.S. government bonds and the dollar. U.S. crude oil prices dropped 1.6 percent to $106.37 a barrel as increased supply from Saudi Arabia and a return to pre-war exports from Libya eased pressure on the market. Key U.S. stock indexes opened more than half a percentage point lower, with the S&P 500 sliding 0.7 percent after closing less than 10 percent shy of its 2007 all-time high. "It seems like a market that probably just needs to take a rest, but I wouldn't be surprised (if) we rally into the day," said Jack Ablin, chief investment officer at Harris Private Bank in Chicago. "It is now a focus back on the fundamentals on the economy and those news items aren't quite as daunting, it's really just fine tuning." After about 20 minutes into the trading session, the Dow Jones industrial average was down 112.46 points, or 0.85 percent, at 13,126.67. The Standard & Poor's 500 Index fell 12.01 points, or 0.85 percent, at 1,397.74. The Nasdaq Composite Index declined 27.39 points, or 0.89 percent, at 3,050.93. World stocks measured by the MSCI All-Country World Index dropped 0.98 percent, after closing near levels last seen in late July. In Europe, the FTSEurofirst 300 index fell 1.14 percent as autos and miners were hit by worries of a China slowdown. The dollar rose 0.41 percent against a basket of major trading-partner currencies, according to the U.S. Dollar Index . Benchmark 10-year Treasury notes were trading 12/32 higher in price to yield 2.34 percent, down from 2.38 percent late Monday, while 30-year bonds gained 23/32 to yield 3.44 percent, down from 3.48 percent.