Oil prices fell on Monday, extending steep losses from the previous session, as Iran and six world powers tried to reach a deal that could add oil to the market if sanctions against Tehran are lifted. Benchmark Brent crude futures (LCOc1) had dropped to $56.04 by 0320 GMT, down 37 cents after falling 5 percent on Friday as the market began to price in the possibility of a deal with Iran. Front-month U.S. West Texas Intermediate (WTI) futures (CLc1) were down 76 cents to $48.11 a barrel.