VIENNA (AP) -- Negotiations over Iran's nuclear program entered their 17th - and possibly last - day in Vienna on Monday as diplomats continued to haggle over details ahead of the expiration of an interim accord.


With the 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 with several issues still unresolved.


And, some said it was possible 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.


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 began expressing optimism that a deal was in reach on Sunday.


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.


French Foreign Minister Laurent Fabius told reporters on Sunday that he believed the negotiations were entering their "last phase."


In Iran, President Hassan Rouhani said an agreement was close, but not quite done, describing the negotiations as "still steps away from reaching the intended peak."


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.


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 backburner have led to new disputes. Among them is 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.


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.


By AP