VIENNA (AP) -- Disputes over attempts to probe Tehran's alleged work on nuclear weapons unexpectedly persisted at Iran nuclear talks on Monday, diplomats said, threatening plans to wrap up a deal by midnight — the latest in a series of deadlines for the negotiations.
The diplomats said two other issues still needed final agreement — Iran's demand for a lifting of a U.N. arms embargo and its insistence that any U.N. Security Council resolution approving the nuclear deal be written in a way that stops describing Iran's nuclear activities as illegal. They demanded anonymity because they are not authorized to discuss the negotiations.
With a temporary deal set to expire at midnight Monday Vienna time (6 p.m. ET), diplomats said they hoped to complete and announce a final agreement before day's end.
But they warned there was no guarantee, and some said the talks could stretch into Tuesday despite there being little appetite for what would be a fourth extension of the interim agreement since the current round began on June 27.
Grim-faced foreign ministers from the countries negotiating with Iran declined to answer questions about another possible extension as they gathered for a group meeting at the 19th Century palace that has been hosting the talks.
"No one is thinking of another extension," Alireza Miryousefi, a spokesman for the Iranian delegation, said on Twitter. "Everyone working hard to get to yes today, but political will (is) still required."
One of the diplomats said the delay posed by the disputes was unexpected, with negotiators expecting that they would be resolved by late Sunday.
Beyond placing long-term limits on Iran's present nuclear program, the United States wants to ensure that the U.N.'s International Atomic Energy Agency has wide-ranging authority to investigate the nuclear arms allegations after nearly a decade of being essentially stalemated.
IAEA chief Yukiya Amano came back from Tehran and talks with Iranian leaders early this month saying that a new plan had been drawn up to aid his probe. Diplomats had earlier said that there was also progress within the Vienna negotiations on the issue. But the debate about how much access his experts should be given has publicly continued, with top Iranian officials saying military sites and Iranian nuclear scientists would be off limits to IAEA experts.
Iran insists it never worked on such weapons and may also be resisting any mention of concessions on the probe in any public documents describing the deal.
Iran's deputy foreign minister, Abbas Aragchi, told reporters in Vienna that the talks are at their "final breathtaking moments (but) certain issues still remain." He said he could not guarantee an agreement would be reached either Monday or Tuesday.
In Brussels, French President Francois Hollande said the sides are near agreement but "a gap" remains.
The foreign ministers of Russia and China, who had left the talks last week, both returned to the Austrian capital late Sunday, and most other foreign ministers of the seven nations at the table also were in Vienna by Monday, in place for any announcement.
"The foreign ministers are gathered to bring negotiations to a conclusion," said Chinese Foreign Minister Wang Yi. "We believe there could not be further delay."
After more than two weeks of see-saw developments, including threats from both the United States and Iran to walk away, senior officials at the talks had begun to express optimism on Sunday that a deal was within reach.
U.S. Secretary of State John Kerry said twice that he was "hopeful" and met again with Iran's Foreign Minister Mohammad Javad Zarif on Sunday evening. After that meeting, foreign ministers and senior officials from the five permanent members of the U.N. Security Council and Germany held a group dinner.
Movement toward a deal has been marked by nearly a decade of wearying negotiations. The pact is meant to impose long-term, verifiable limits on nuclear programs that Tehran could modify to produce weapons. Iran, in return, would get tens of billions of dollars in sanctions relief.
Meanwhile, Israeli Defense Minister Moshe Yaalon said that the nuclear deal would force the Jewish state to "defend itself, by itself."