Iran informed the six major powers on Friday it would not accept their "excessive demands" after the latest talks on a permanent nuclear deal ended with no breakthrough, Reuters reports.
Iran and the United States, Russia, China, France, Britain and Germany are striving to turn an interim deal signed in November into a comprehensive settlement by July 20.
Under the interim deal, Iran committed to limit its uranium enrichment to five percent and is gradually winning access to $4.2 billion of its oil revenues frozen abroad and some other sanctions relief.
It looks like it will not be easy, as Iranian Foreign Minister Mohammad Javad Zarif on Friday urged the six nations to "abandon excessive demands which will not be accepted by Iran."
"Still we have not overcome disputes about major issues," Zarif told reporters as five days of negotiations in Vienna wound up, according to Reuters.
"There has been progress, but major disputes remain," he added.
Zarif made clear there was no agreement yet between Iran and the six on a draft text of an agreement. A senior Chinese official said the two sides had put together a "textual framework", though gave no details.
"The fact that (we came up) with this text is progress ... in procedural terms," China's Wang Qun told reporters.
Diplomats from the six powers told Reuters earlier in the week that one of the most difficult issues in the talks was the number of centrifuges Tehran will be allowed to keep to enrich uranium under any deal.
Western officials say that the six powers want this number to be in the low thousands to prevent any Iranian dash to a nuclear bomb-making capability. Iran insists on tens of thousands of centrifuges to make fuel for what it says is a panned network of civilian nuclear power stations.
A spokesman for European Union foreign policy chief Catherine Ashton, who coordinates the talks, would only say that the two sides had begun drafting the text of a deal during their fifth round of negotiations this year.
"We have worked extremely hard all week to develop elements we can bring together when we meet for the next round in Vienna, beginning on July 2," Michael Mann said in a statement.
"We presented each other with a number of ideas on a range of issues, and we have begun the drafting process."
Zarif indicated this week that the sides have started drafting a comprehensive agreement but added “there are still many differences” over the text.
The powers are seeking a settlement that would limit Iran's nuclear program. Throughout the talks, Iran has declared that it will never give up on what it sees as its right to uranium enrichment.