The United States and European powers have voiced disappointment at what they said was Iran's lack of seriousness in the latest round of negotiations on reviving a landmark 2015 nuclear deal.
The talks between Iran and the remaining parties to the nuclear agreement -- Britain, France, and Germany (known as the E3), China, and Russia -- were resumed on November 29 in Vienna after a five-month hiatus, with the United States participating indirectly.
U.S. Secretary of State Antony Blinken said on December 3 that the talks were paused because Iran does not seem to be serious about doing what is necessary to return to compliance with the deal.
Speaking at a conference in Washington, Blinken said the United States would not allow Iran to draw out negotiations while continuing to advance its nuclear program, warning that Washington will pursue other options if diplomacy fails.
"What we've seen in the last couple of days is that Iran right now does not seem to be serious about doing what's necessary to return to compliance, which is why we ended this round of talks in Vienna," Blinken said.
"We're going to be consulting very closely and carefully with all of our partners in the process itself...and we will see if Iran has any interest in engaging seriously," he said.
The European Union official chairing the meeting said there had been some progress, but further "convergence" was necessary.
"We have identified the challenges ahead. Now it is time to consult with capitals," EU diplomat Enrique Mora told reporters. "We will be resuming here in Vienna next week."
"We have substantial challenges ahead, time is not unlimited, there is an obvious sense of urgency," he added. "But above all we need a certain convergence of policy to start negotiations."
Diplomats are aiming to revive the Joint Comprehensive Plan of Action (JCPOA) which began unraveling in 2018 when former U.S. President Donald Trump pulled out of the deal and reimposed sanctions, prompting Iran to exceed limits on its nuclear program.
Trump's successor, Joe Biden, has said the United States is ready to rejoin the JCPOA, provided Iran resumes observing the deal's conditions.
Senior E3 diplomats in a statement expressed "disappointment and concern" in the negotiations after Iran proposed changes to the text negotiated during the previous six rounds, which started in April and were suspended in June when Iran elected a new president.
"Major changes [have been] demanded [by Iran]," the officials said in a statement, adding that some were incompatible with the 2015 deal.
"Tehran is walking back almost all of the difficult compromises crafted after many months of hard work," they added.
The E3 diplomats went on to say it was "unclear how these new gaps can be closed in a realistic time frame."
White House Press Secretary Jen Psaki accused Iran of failing to come to Vienna with "constructive proposals."
But Iran's top negotiator sounded a defiant note in response to Western criticism, saying the European side can propose their own drafts for discussion, state media reported.
"There is no problem if the Europeans also provide drafts, and they can be discussed, but they must be based on principles approved by both sides," Ali Bagheri Kani said, according to state broadcaster IRIB, before leaving Vienna.
Among other things, Iran is demanding the lifting of all U.S. sanctions and guarantees that Washington will not withdraw from any future agreement.
Iran's semiofficial ISNA news agency said the talks would "most likely" resume on December 6, but French President Emmanuel Macron warned there could be a longer break in the talks.