Oil prices fell in Asia Wednesday after Russia and Iran's foreign ministers claimed a breakthrough in talks over Tehran's controversial nuclear programme that could ease sanctions on the crude producer.
US benchmark West Texas Intermediate (WTI) for May delivery eased 15 cents to $47.45, while Brent crude for May fell five cents to $55.06 in afternoon trade.
"The nuclear talks with Iran extended over the deadline. However, it seems to lean towards an agreement," said Daniel Ang, investment analyst with Phillip Futures in Singapore.
"Iran produces a high volume of crude and if the sanctions are eventually lifted, this will push both the WTI and Brent downwards for a prolonged period," he said.
Russia's Sergei Lavrov and Iran's Mohammad Javad Zarif said Wednesday that they and foreign ministers of five other major powers would work through the night to agree the main outline of what they hope will be an historic accord.
The United States, China, Britain, Russia, France and Germany hope a full agreement, due to be finalised by June 30, will see Iran scale back its nuclear capability to prevent Tehran developing nuclear weapons under the guise of its civilian programme.
In return, diplomatically isolated Tehran, which denies wanting atomic weapons, is demanding the lifting of sanctions that have strangled its economy.
A deadline of midnight on Tuesday was scrapped after the US insisted enough progress had been made to warrant extending the marathon talks.
With the world's fourth-biggest oil and second-biggest gas reserves, the energy industry is the cornerstone of Iran's economy, but it has been hit hard by the American and European embargo imposed since 2012.
Crude dealers, meanwhile, are awaiting the latest official US stockpiles report to be released later Wednesday for clues about demand in the world's top consumer, analysts said.
Oil reserves likely rose by 4.2 million barrels in the week ending March 27, according to a survey by Bloomberg News.