VIENNA/TEHRAN - Negotiators plan to announce on Monday that they have reached agreement on a historic deal on Iran’s nuclear program, diplomats told The Associated Press on Sunday.

The two diplomats said that a provisional agreement may be reached even earlier — by late Sunday. But they cautioned that final details of the pact were still being worked out and a formal agreement still awaits a review from the capitals of the seven nations at the talks.

And senior U.S. and Iranian officials suggested that not enough time was left to reach a provisional deal by Sunday. All of the officials, who are at the talks, demanded anonymity because they weren’t authorized to discuss the negotiations publicly.

“We are working hard, but a deal tonight is simply logistically impossible,” the Iranian official said, noting that the agreement will run roughly 100 pages with five technical annexes.

The senior U.S. official declined to speculate as to the timing of any agreement or announcement and noted that “major issues remain to be resolved in these talks.”

Movement toward a deal has been marked by years of tough negotiations. The current round in Vienna has run more than two weeks and blown through three deadlines.

Even before the envoys spoke to the AP, the nuclear negotiations appeared on the way to an agreement.

U.S. Secretary of State John Kerry, who on Thursday had threatened to walk away from the negotiations, noted Sunday that “a few tough things” remain in the way but added “we’re getting to some real decisions.”

En route to Mass at Vienna’s gothic St. Stephens Cathedral, Kerry said twice he was “hopeful” after a “very good meeting” Saturday with Iranian Foreign Minister Mohammad Javad Zarif, who had Muslim services Friday.

French Foreign Minister Laurent Fabius also was cautiously optimistic, telling reporters Sunday: “I hope, I hope, that we are finally entering the last phase of this marathon negotiation.”

“I believe it,” he added. “France’s position has been one of constructive firmness and I hope it will allow is to reach the end now, quickly, for a satisfying result.”

A senior Iranian official also said an agreement was close.

“The deal is within reach today,” the official told Reuters. “But some issues remain that need to be resolved by foreign ministers.”

The pact is meant to impose verifiable limits on Iran’s nuclear programs. Iran, in return, would get tens of billions of dollars in sanctions relief.

The current round of nuclear talks is now in its 16th day and has been extended three times since the first deadline of March 31 was missed. The mood among negotiators had turned more somber each time a new target date was set.

As the weekend approached, Kerry declared the talks couldn’t go on indefinitely and warned that the U.S. could walk away from the negotiations.

But in another sign that a deal could soon be sealed, Russian news agencies reported that Russian Foreign Minister Sergey Lavrov planned to arrive in Vienna on Sunday evening.

Most other foreign ministers of the six nations negotiating with Iran already were in the Austrian capital and in position to join Kerry and Zarif for any announcement of an agreement.

Diplomats familiar with the talks said most of the nuts and bolts of implementing the deal have been agreed upon. But over the past week, issues that were previously on the back burner have led to new disputes.

Among them was Iran’s demand for a lifting of a UN arms embargo and its insistence that any UN Security Council resolution approving the deal be written in a way that stops describing its nuclear activities as illegal.
A diplomat familiar with the negotiations said disagreements also persist on how long some of the restrictions on imports of nuclear technology and other embargos outlined in any new Security Council resolution will last. The diplomat, who demanded anonymity because the diplomat wasn’t allowed to discuss the confidential talks, said restrictions will last for years, not months.

Kerry and Zarif have met nearly every day since Kerry arrived in Vienna more than two weeks ago for what was intended to be the final phase in a negotiation process that began with an interim nuclear deal clinched in November 2013.

Experts and senior officials from Iran, the United States and the other powers have been meeting non-stop for months, often working into the early hours of the morning.

An agreement would be the biggest step toward rapprochement between Iran and the West since the 1979 Islamic Revolution, although both sides are likely to remain wary of each other even if a deal is concluded.

MD/PA