A rebound in oil prices faltered on Wednesday as U.S. data showed a rise in crude inventories, while U.S. and European shares gave up earlier gains.

The retreat in oil prices cut short a rally in commodities and equities that had been fuelled by better-than-feared Chinese trade data, which relieved concerns about the health of world's second-largest economy.

Major U.S. indexes fell in morning trading after opening higher. The pan-European FTSEurofirst 300 index was up 0.3 percent.

"People have seen in the past that these oil rallies have been very short, and to the extent they influence the equity markets, there is certainly some profit-taking going on," said Rick Meckler, president of LibertyView Capital Management in Jersey City, New Jersey.

"People are selling every rally that is based on the movement of oil, because by the end of the day it can turn around and be down another 5 percent," Meckler said.

Concern about a supply glut has helped drag down oil prices to 12-year low and crude dipped below $30 a barrel on Tuesday.

U.S. crude futures plunged as much as 4 percent, or $1.25 a barrel, following release of U.S. government data showing a large surge in gasoline and diesel stockpiles. Prices fell as low as $30.10 a barrel.

U.S. crude prices were last up 1.2 percent at $30.75 a barrel, while benchmark Brent was down 0.5 percent at $30.73 a barrel.

The Dow Jones industrial average fell 38.42 points, or 0.23 percent, at 16,477.8, the S&P 500 lost 2.88 points, or 0.15 percent, at 1,935.8 and the Nasdaq Composite dropped 21.76 points, or 0.46 percent, at 4,664.16.

"The risk markets, near-term, are still going to be paying closest attention to the price of oil," said Mark Heppenstall, chief investment office of Penn Mutual Asset Management in Horsham, Pennsylvania.

European shares were helped by a rise in Dutch insurer Aegon following a business update.

MSCI's broadest gauge of stocks globally rose 0.4 percent.

Investors were also encouraged by data out of China. Exports from the country fell 1.4 percent from a year earlier, data from the General Administration of Customs showed. That was better than a Reuters poll forecast an 8-percent drop and moderated from November's 6.8-percent decline.

The U.S. dollar was up 0.03 percent against a basket of currencies, while the euro was up 0.05 percent against the dollar.

"The broader market tone is showing signs of tentative risk appetite, bolstered by continued stability in China's exchange rate and reinforced by the release of better-than-feared trade figures out of China," said Eric Theoret, currency strategist, at Scotiabank in Toronto.

Benchmark 10-year U.S. Treasury notes fell 4/32 in price to yield 2.1137 percent, from 2.1 percent late on Tuesday.