Oil prices edge lower as Iran nuclear deadline approaches

Oil prices fell in Asia on Tuesday as dealers monitored last-ditch efforts between global powers and Iran to reach a deal on Tehran's nuclear programme and ease sanctions imposed on the crude producer.

US benchmark West Texas Intermediate fell 69 cents to USD 47.99 while Brent eased 55 cents to USD 55.74 in mid-day trade. Singapore United Overseas Bank said prices "tumbled as hopes for a nuclear deal with Iran climbed".

Foreign ministers of US-led major world powers are racing to beat a midnight deadline to nail down a framework deal with Iran they hope will put an atomic bomb out of the Islamic republic's reach.

"There are marathon meetings happening all over the place. There are several issues that have not been resolved yet.

These are important issues," an Iranian negotiator in the Swiss city of Lausanne said late Monday. US Secretary of State John Kerry, in Lausanne since Wednesday for the latest in a series of meetings with Iranian counterpart Mohammad Javad Zarif that have criss-crossed the globe, said Monday there was still work to do. "There still remain some difficult issues," Kerry told CNN.

"We are working very hard to work those through. We are working late into the night and obviously into tomorrow." Under the deal, due to be finalised by June 30, the powers want Iran to scale back its nuclear programme to give the world ample notice of any dash to make a bomb by extending the so-called "breakout" time.

In return diplomatically isolated Tehran, which denies wanting atomic weapons, is demanding the lifting of sanctions that have strangled its economy.

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.