Brent crude, the global benchmark, was down 0.69 cents, or about 1 percent, at $68.33 a barrel by 0244 GMT, a nearly two-week low.

U.S. West Texas Intermediate (WTI) futures were down, 67 cents, or 1 percent, at $63.83, after falling to its weakest level in more than a week. 

On Tuesday, U.S. crude fell 1.6 percent to close at $64.50 a barrel, the contract’s decline far outpacing a 0.6 percent drop in the price of Brent.

“Increasing concerns over the rising U.S. production continue to mount pressure on the commodity,” said Mihir Kapadia, chief executive of Sun Global Investments. “Over the past couple of years, U.S. producers have gained significant inroads in the global oil market industry,” he said.

Prices on both WTI and Brent are still on track for a fifth month of gains.

But the report from the American Petroleum Institute late on Tuesday showing crude stocks rose by 3.2 million barrels last week cast a further bearish pall over the market. [API/S]

It came after data showed that U.S. energy companies added 12 oil rigs last week, the biggest weekly increase since March. 

U.S. Energy Department data on Wednesday is likely to show an increase in increase in inventories for the first time 11 weeks. Analysts polled by Reuters forecast an average 100,000-barrel build in crude stocks. [EIA/S]

The date is due out at 10:30 a.m. EST (1530 GMT) on Wednesday.