John Kerry attends nuclear talks in Switzerland
John Kerry attends nuclear talks in SwitzerlandReuters

For the first time since breaking his leg in a bicycle accident in France, U.S. Secretary of State John Kerry will take part in Iran nuclear talks, State Department spokesman John Kirby said in a statement on Wednesday.

Kirby said that Kerry will fly to Vienna on Friday to take part in the talks as the sides continue to try and reach an agreement by a June 30 deadline.

Speaking later on Wednesday, Kerry said that nuclear negotiations with Iran will not be affected by recent comments from Iran's supreme leader who appeared to backtrack on key points of an emerging deal, according to The Associated Press (AP).

Kerry referred to this week's speech by Ayatollah Ali Khamenei, in which he ruled out Iran freezing sensitive nuclear work for a lengthy time period as part of the deal, but said the speech would not deter the talks.

Kerry said the speech, along with highlights on Khamenei's official Twitter feed were for "domestic political consumption," according to AP. And, he said that if Iran did backtrack on commitments made in an April outline there would be no deal.

"This is something that's been going on throughout the negotiations," Kerry said of the Iranian leader's remarks. "It is not new. We are not going to be guided by or conditioned by or affected or deterred by some Tweet that is for public consumption or domestic political consumption. What matters to us is what is agreed upon within the four corners of a document and that is what is yet to be determined."

"It may be that the Iranians will not fill out the full measure of what was agreed at Lausanne and, in that case, there will not be an agreement," he continued, referring to the framework reached on April 2 in Lausanne, Switzerland.

Kerry said neither he nor President Barack Obama the United States would negotiate in public.

"I am not tweeting," he said, according to AP. "I am not making speeches, neither is President Obama."

The comments come amid disagreement over many remaining issues in the talks between Iran and the six world powers.

In fact, two diplomats said last week that the sides are still apart on all main elements of the nuclear deal, describing the draft of a main document as a patchwork of text and dozens of blank spaces because of stubborn disagreement on up to 10 crucial points.

The comments are in line with ones made by a diplomat who had spoken with a Russian news agency and said the talks are “virtually stalled”.

Among the unresolved issues are the pace of easing Western sanctions imposed over the Iranian program and the monitoring and verification measures to ensure Iran could not pursue a clandestine nuclear weapons program.

Iran has categorically deniedreports that it would allow inspectors into its sites as part of a final deal, describing them as mere rumors and as wrong interpretations of the understanding reached in early April.

Iran’s Deputy Chief of Staff recently reiteratedthat the Islamic Republic will not allow any inspection of its military sites, calling the demand to do so “excessive”.

In addition, UN inspectors regularly monitor Iran's declared nuclear facilities, but the International Atomic Energy Agency (IAEA) has complained for years that Iran is not complying with its probe into its past nuclear activities.

And, in a move that potentially will complicate chances for the final deal with the six powers, Iran's parliament passed a bill on Tuesday banning access for IAEA inspectors to its military sites and scientists.