Nuclear deal not in sight

The United States and Iran sought Sunday to bridge gaps in negotiations on the eve of a deadline for a nuclear deal, as Iran signalled it was open to extending the talks by up to a year.

US Secretary of State John Kerry went into a fifth round of talks in Vienna with his Iranian counterpart Mohammad Javad Zarif ahead of Monday's deadline.

The two key players in the protracted on-off negotiations have been trying since Thursday to secure a deal that would curb Iran's disputed nuclear activities in exchange for broad relief from punishing international sanctions.

It could end a 12-year standoff that has even raised the prospect of Israeli military strikes on Iranian nuclear facilities. Kerry spoke to Israel's Prime Minister Benjamin Netanyahu by phone on Saturday.

"We're working hard," Kerry said Saturday in Vienna. "And we hope we're making careful progress, but we have big gaps, we still have some serious gaps, which we're working to close."

German Foreign Minister Frank-Walter Steinmeier, also in the Austrian capital, called the weekend of talks a "moment of truth".

An Iranian source told AFP that Tehran is open to having the nuclear negotiations extended by six months or a year if no real progress towards an agreement is achieved later Sunday.

Such an extension would be under the terms of an interim accord reached in Geneva a year ago that traded a temporary freeze on some aspects of Iran's nuclear activities for limited sanctions relief, the source said.

The five permanent members of the UN Security Council -- Britain, China, France, Russia and United States plus Germany -- the so-called P5+1 -- have been locked in talks with Iran since February to turn the interim Geneva accord into a lasting agreement.

Such a deal is aimed at easing fears that Tehran will develop nuclear weapons under the guise of its civilian activities.

The Islamic Republic hotly denies it wants to build the bomb and insists its programme is entirely peaceful.

A European source at the talks said there had been "no significant progress" and that "the chances of getting a deal are pretty reduced".

"In order to get a deal the Iranians will have to budge in a rather substantial manner," he said.

Many experts believe that the deadline may be extended, as happened with an earlier cut-off point on July 20, but officials insist that this is not on the table -- yet.

Russian Foreign Minister Sergei Lavrov, a key player in the talks, is expected in Vienna late yesterday, RIA Novosti state news agency reported, citing a diplomat.