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Iran Nuclear Talks to Extend Past June 30 Deadline: Official

Negotiations over Iran's nuclear program will miss Tuesday's deadline for a deal, a senior U.S. official said Sunday.

VIENNA — Negotiations over Iran's nuclear program will miss Tuesday's deadline for a deal, a senior U.S. official said Sunday, as Tehran’s foreign minister jetted home for consultations with his government.

News that Foreign Minister Mohammad Javad Zarif was heading back to Tehran for 24 hours came following a meeting with U.S. Secretary of State John Kerry in Vienna — their third encounter since Saturday. Zarif, Kerry and their counterparts have been working around the clock to reach an agreement ahead of a June 30 deadline.

A senior U.S. official said after the meeting that "some progress" had been made in the talks but "a number of unresolved issues" remained between Iran and the six world powers, known as the P5+1.

Related: Where Things Stand on Iran Nuclear Talks

"It is fair to say the parties are planning on staying past June 30th to keep negotiating as we have always said we may have to," the official said, speaking on condition of anonymity.

However, the official cautioned that "no one is talking about some kind of long term extension" but rather "a few extra days."

Going into the Vienna talks it was unclear if the sides would be able to bridge disagreements to meet Tuesday’s deadline, with all sides acknowledging challenges remained. Chief among the obstacles, U.S. officials say, is access for United Nations nuclear inspectors to military sites to verify that Iran is complying with peaceful purposes for nuclear-related research and development.

Britain's Foreign Secretary Philip Hammond said that "no deal is better than a bad deal" as he arrived for talks, while the European Union's High Representative Federica Mogherini expressed cautious optimism.

"If all negotiating parties have strong political will in these last moments,we can make it," she said on Twitter.

Still, the framework agreement reached in April itself seemed in jeopardy following comments this week by Iran's supreme leader.

Ayatollah Khamenei, who has the final say on the future of Iran's nuclear program, said in a speech Tuesday the sanctions on his country should be lifted immediately as soon as any deal is signed. His comments appeared to go against the framework agreement reached by Iran and the six nations which said sanctions would be gradually phased out based on Iran's compliance with any deal.

However, Iranian officials in Vienna over the weekend indicated there could be some room for interpretation. They say there has been basic agreement on sanctions relief in three stages — and that the Supreme Leader could be calling for full sanctions relief at that third stage, several months from now, once a deal is fully operational.

U.S. negotiators hope that Zarif will be able to get that kind of clarification nailed down while he is in Tehran.

NBC News has also learned that a key Iranian player in the talks, Ali Akbar Salehi — the head of Iran’s atomic energy organization — will possibly return to the talks with Zarif.

His relationship with U.S. Energy Secretary Ernest Moniz, Kerry’s partner in the talks, was a key factor in reaching the April provisional agreement. U.S. officials have said that Salehi was recovering from surgery. The talks have been injury-plagued: Kerry is negotiating with a broken leg, hampering his ability to move around Vienna on this trip.

As the diplomats in Vienna raced against the clock, Israel's Prime Minister Benjamin Netanyahu warned that there has been a "stark retreat" from red lines set by world powers in relation to Iran's nuclear program.

"The concessions being made to Iran are growing," he told a weekly cabinet meeting. "There is no reason to hasten into signing this bad deal, which is getting worse by the day."