(TEHRAN, Iran) -- Iran has agreed to restart negotiations over its nuclear program next month, its chief negotiator said Wednesday.
Those talks, in which Iran and the U.S. have engaged through intermediaries, come as the Obama-era nuclear deal hangs by a thread and amid warnings about Iran's nuclear advances since Iran halted talks in June.
It's unclear whether an agreement has been reached to resume talks, when they would begin and whether Iran still has preconditions like sanctions relief. Iran's top negotiator, deputy foreign minister Ali Bagheri Kani, said the "exact date will be announced next week."
A State Department spokesperson told ABC News the administration had "seen the reports but do not have any further details about a possible return to Vienna talks in November."
Iran had halted those talks in the Austrian capital right before its presidential election in June, saying for months now that the new administration of hardliner Ebrahim Raisi needed time to transition and formulate his team.
But during that halt, Iran has advanced its nuclear program -- expanding its stockpile of enriched uranium, enriching uranium to higher levels, spinning more centrifuges and more advanced ones -- alarming U.S. officials.
It has also obstructed the work of the U.N. nuclear watchdog, the International Atomic Energy Agency, or IAEA, whose chief said last week its monitoring ability is "no longer intact."
The Biden administration has increasingly warned that while the door is still open to diplomacy, time is running out before restoring the deal would be pointless because of how advanced Iran's nuclear program had become.
"This window will not remain open forever as Iran continues to take provocative nuclear steps, so we hope that they come to Vienna to negotiate quickly and in good faith," the State Department spokesperson said Wednesday in a statement.
To critics, that window should have already been closed, while many analysts warned that Iran is still stalling, even as it talks about resuming negotiations.
"If they continue to stall while advancing their nuclear program, there may come a time when the U.S. or Israel turn to 'plan B'," tweeted Nicholas Miller, a Dartmouth College professor who researches nuclear proliferation.
The top U.S. negotiator, special envoy for Iran Rob Malley, said Monday there's "shared impatience" with Iran among the U.S. and other negotiating parties -- Russia, China, France, Germany, the United Kingdom and the European Union, which coordinated the previous six rounds of talks.
"Time is not on our side. The JCPOA cannot survive forever," Malley added, using an acronym for the nuclear deal's formal name.
But there's still a "strong preference for diplomacy, for an effort to revive the JCPOA," he said, and said there's "willingness" and "determination" from the Biden administration to make it happen.
On Wednesday, Bagheri met with Enrique Mora, a senior European Union diplomat who had been facilitating the talks. After their "serious and constructive conversation," Bagheri tweeted, Iran "agreed to start negotiations by the end of November."
But his boss, Iranian Foreign Minister Hossein Amir Abdollahian, also said Wednesday that while Iran would restart talks, it would not resume them with what had been agreed upon by June -- jettisoning months of previous negotiations. He also called on the U.S. to release $10 billion of Iranian funds frozen by U.S. sanctions to build confidence ahead of any agreement.
That's a sign of how far apart the new U.S. and Iranian governments are. Even if the parties convene again in Vienna, it will be a long road ahead to revive the deal.
As Abdollahian reiterated, Iran has demanded that the U.S. lift sanctions first, since it was former President Donald Trump who first violated the deal by exiting and reimposing sanctions. But President Joe Biden has committed to not lifting any sanctions until Iran returns to compliance -- what his administration calls a "mutual return" to the deal -- amid continued domestic criticism of the original agreement in Washington.
In the meantime, as Iranian centrifuges continue to spin, Iran hawks in the U.S. and Israel warn that it's too late for diplomacy and that other options, including a possible military strike, must be considered.
Secretary of State Antony Blinken has not engaged questions about a strike but told reporters two weeks ago the Biden administration was considering "every option to deal with the challenge posed by Iran."
"We, of course, retain all other options to be able to deal with this program as necessary," National Security Advisor Jake Sullivan said Tuesday. "But beyond that, I'm not going to comment further because we believe there still is an opportunity to resolve this diplomatically."