Iran says Western powers backtracking as nuclear deadline expire

Iran accused major powers on Friday of backtracking on previous pledges and throwing up new "red lines" at nuclear talks, after the deadline to reach an agreement in time to receive expedited scrutiny from the U.S. Congress expired with no deal.

Iran's foreign minister Mohammad Javad Zarif said a deal was unlikely to be reached on Friday and negotiators would probably spend the weekend in Vienna.

"Now, they have excessive demands," he said of the powers' negotiating position.

Zarif has been holding intense meetings for more than two weeks with U.S. Secretary of State John Kerry to try to hammer out a final agreement limiting Iran's nuclear programme in return for withdrawing economic sanctions.

They have been joined periodically by foreign ministers from Britain, China, France, German and Russia, also party to any deal, which would be the biggest step towards rapprochement between Iran and the West since the 1979 Islamic Revolution.

But the negotiations have become bogged down, with final deadlines extended twice in the past 10 days and diplomats speaking of heated exchanges between Kerry and Zarif.

Because no deal was complete by Friday morning, any agreement would now be subject to 60 days of scrutiny by the sceptical, Republican-dominated U.S. Congress, rather than an expedited 30 day review.