Dragging on: oil prices down 4 percent

Oil prices fell as much as 4 per cent on Thursday after global powers negotiating a nuclear deal with Iran called for a news conference after more than a week of talks in Switzerland.

A nuclear pact for Tehran could remove Western sanctions on the Opec nation's oil exports, bringing millions of additional Iranian crude barrels onto a market already brimming with supply.

A European representative told reporters there will be a press event on Iran's nuclear program at an unspecified time in the Swiss city of Lausanne, where the talks have been taking place. The reporters were told to move to news conference site immediately.

A joint statement is being finalised between Iranian Foreign Minister Javad Zarif and EU foreign policy chief Federica Mogherini, a Western diplomat said on Thursday.

North Sea Brent crude futures, the more widely-used global benchmark for oil, were down $2.50, or 4.3 per cent, by 11:27 am EDT (1527 GMT) at $54.60, after hitting a session low of $54.45 on the news of the press conference.

US crude futures were down $1.30, or 2.6 per cent, at $48.79 a barrel, after falling more than $1.70 earlier.