Senior diplomats from France, Britain and Germany said Iran has demanded major changes, some of which were incompatible with the 2015 deal.
Negotiations in Vienna aimed at reviving the Iran nuclear deal will be suspended as European diplomats expressed "disappointment and concern" at the latest proposals from Iran.
The semi-official ISNA news agency said the talks suspended on Friday would "most likely" resume on Monday, but French President Emmanuel Macron warned there could be a longer break in the talks, which resumed only on November 29 after a five-month break.
Iran said it has submitted two draft proposals for the nuclear agreement, which has been in tatters since the US withdrew in 2018.
"After the handing over of the text of the Iranian proposal to the P4+1 group (Britain, China, France and Russia plus Germany) and the European Union, a meeting of the joint committee of the nuclear deal will be held on Friday," said Iran's official news agency IRNA.
"This meeting was requested by the European side before its representatives return to their capitals to review the text proposed by Iran," the news agency added.
Senior diplomats from the E3 group of Britain, France and Germany expressed "disappointment and concern after thoroughly and carefully analysing Iranian proposed changes to the text negotiated during the previous six rounds", which took place earlier this year.
"Major changes (have been) demanded (by Iran)," the officials said in a statement, adding that some were incompatible with the 2015 deal.
It is "unclear how these new gaps can be closed in a realistic timeframe on the basis of Iranian drafts," they said.
On Thursday, Iran's lead negotiator Ali Bagheri said the proposals concerned two main issues facing the 2015 accord known as the Joint Comprehensive Plan of Action, or JCPOA.
"The first document sums up the Islamic republic's point of view concerning the lifting of sanctions, while the second is about Iran's nuclear actions," Bagheri told state TV.
"Now the other side must examine these documents and prepare itself to hold negotiations with Iran based on these documents."
In a telephone call with EU top diplomat Josep Borrell, Foreign Minister Hossein Amir Abdollahian said the talks were going well "but slowly on all tracks".
"We think that a good agreement is possible but that requires a change of approach by certain parties who must drop their threatening language and opt for texts focused on cooperation, mutual respect and results," the minister said.
The talks had resumed in the Austrian capital on Monday after Iran paused them in June following the election of ultraconservative President Ebrahim Raisi.
The goal of the JCPOA is to make it practically impossible for Iran to build an atomic bomb, while allowing it to pursue a civilian nuclear programme. Iran has always denied wanting a nuclear arsenal.