Oil prices fell Thursday as worries that global supply might surpass demand persisted.

Crude production from the Organization of Petroleum Exporting Countries (OPEC) increased by 101,000 barrels per day to average 31.51 million barrels per day in July, according to OPEC monthly oil market report released Tuesday.

Iran and six of the world's major countries have adopted an agreement on the Iran nuclear issue. Traders worried that more Iranian crude would come to the already well-supplied oil market.

The OPEC maintained its output quota of 30 million barrels per day at June's meeting. The cartel's output accounted for around 40 percent of the global crude output.

U.S. dollar rises on upbeat data Thursday. A stronger greenback made the dollar-priced crude more expensive and less attractive for buyers holding other currencies.

The West Texas Intermediate for September delivery moved down 1. 07 U.S. dollars to settle at 42.23 dollars a barrel on the New York Mercantile Exchange, while Brent crude for September delivery decreased 44 cents to close at 49.22 dollars a barrel on the London ICE Future Exchange.