News that energy firms in the US regulated areas of the Gulf of Mexico had shut some 22 percent of crude oil equivalent output as a precaution to threats from a tropical storm limited some of the downside in crude prices.

Brent crude futures LCOc1 settled down 89 cents, or 1.8 percent, at $48.37 per barrel.

US West Texas Intermediate (WTI) crude futures CLc1 fell 63 cents, or 1.3 percent, to close at $46.35.

It was a second straight day that oil slid on worries of oversupply and a strong dollar, adding to Monday's drop of more than 1 percent in Brent and WTI.

"Today is just another economic story that's fed the dollar's strength and with the weekly build expected in US crude, prices are getting a double whammy," said Tariq Zahir, a trader in WTI timespreads at Tyche Capital Advisors in New York.

"Yes, we have storm concerns but they are not really affecting production as much as the market bulls would like."

After the market settled, the trade group American Petroleum Institute reported that US crude stockpiles rose 942,000 barrels last week, in line with expectations of analysts polled by Reuters. The US government will release official inventory data on Wednesday.

An Iranian government official said at an oil industry conference in Norway that Tehran's production was expected to hit 4 million barrels per day by year end. Iran was producing that much before Western sanctions reduced its exports.

The dollar index .DXY, which measures the greenback against a basket of currencies, hit three-week highs after the US Consumer Expectations Index rose to October highs.

The dollar has rallied since Friday, after Federal Reserve Chair Janet Yellen raised expectations for a US rate hike in a policy speech. A stronger greenback tends to make dollar-denominated commodities such as oil costlier for holders of other currencies.

Oil prices rose about 20 percent earlier in August, after the Organization of the Petroleum Exporting Countries said it was working with non-OPEC members to reach a production freeze. Iraq said on Tuesday it was committed to freezing output when OPEC meets informally for talks with other producers in Alegria next month.