Oil prices fell for the second straight session on Monday as Iran and six world powers negotiated a deal for Tehran's nuclear program that could end Western sanctions, allowing the OPEC member to ship more crude into an already flooded market.
Officials close to the talks have said progress has been made and many investors believe a deal is in the making. Few expect the talks to end without some sort of agreement.
U.S. crude closed down 19 cents at $48.68 a barrel, off an earlier low of $47.61. Brent crude was down 10 cents at $56.31 a barrel after State Department officials said there is a 50/50 chance of a framework agreement with Iran.
"We're likely to stay jittery through the day on any headline coming out of Lausanne, and the stronger dollar isn't helping oil either," said analyst Phil Flynn of Price Futures Group in Chicago.
The dollar rose as the euro slumped on worries over whether Greece would secure aid before it runs out of cash in three weeks. A stronger dollar makes commodities denominated in the greenback, such as oil, more costly for holders of other currencies.