Oil prices fell on Monday as Iran and six world powers were close to nailing down a nuclear deal.
Iran and six world powers are reportedly on the brink of finding a nuclear deal that would bring sanctions relief in exchange for curbs on Tehran's nuclear program.
US crude prices were down 85 cents at $51.89 a barrel at 0433 GMT. Brent crude fell more than a dollar to $57.65 a barrel on worries a deal with Iran would lead to an easing of sanctions against Tehran and to higher crude exports.
"If a deal is confirmed, we may see support broken and the next test at $49.5 (for US crude)," CMC Markets said, Reuters reported.
Although analysts said it would take until 2016 before Iran would be able to return to full-scale exports, most estimate that a jump of around 200,000 barrels per day in exports could be seen in the short term, adding to a current surplus of more than 2.5 million barrels a day.
In Europe, the Greek debt crisis continued as political leaders argued late into the night at an emergency summit, so far without result.
With oversupply ongoing and abundant economic risk, the International Energy Agency and several banks said they had lowered their oil price forecasts.
"The bottom of the market may still be ahead," the IEA said in its monthly report.
Bank of America Merrill Lynch said US crude prices "could soon drop well below our $50 per barrel target in 3015".
Commerzbank said that a fall below $55 per barrel in Brent and below $50 per barrel in US crude was "conceivable".
Oil prices also fell in Asia Monday as Iran and major western powers said they were closer than ever to a landmark nuclear deal that would lift sanctions and see Tehran’s crude exports return to global markets.
"We have come a long way. We need to reach a peak and we are very close," Iranian President Hassan Rouhani said in Tehran on Sunday.
"I hope we are finally entering the final phase of these marathon negotiations. I believe it," said French Foreign Minister Laurent Fabius, who cancelled a trip to Africa to stay at the talks in Vienna.
