Extra demands made by Washington contradict its position on reaching an agreement swiftly, says Iranian FM Hossein Amirabdollahian, without specifying the demands.
Iran has said the United States made extra demands and accused it of working to "complicate" efforts to restore a 2015 nuclear deal after new Russian requests linked to the Ukraine assault raised concerns of fresh delays.
"There is no rational justification for some of the new demands made by the United States, and it contradicts the country's position on reaching an agreement swiftly," Iranian Foreign Minister Hossein Amirabdollahian said in a phone call with EU foreign policy chief Josep Borrell, his ministry reported on Thursday.
Amirabdollahian did not specify the demands but said "the US cannot pass on a new and different message to us every day through the coordinator", in reference to the EU.
Iran's supreme leader Ayatollah Ali Khamenei, who has the final say in major state policies, meanwhile, stressed his country will not give up on elements of "national strength", such as nuclear progress and regional influence.
Tehran is locked in negotiations with world powers to revive the nuclear deal that offered it sanctions relief in return for curbs on its atomic programme.
Its arch-foe the United States, under former president Donald Trump, unilaterally withdrew in 2018 from the accord known formally as the Joint Comprehensive Plan of Action.
Earlier on Thursday, Iran's top security official Ali Shamkhani tweeted that "Vienna negotiations are becoming more complicated every hour without a political decision by the United States."
"US approach to Iran's principled demands, coupled with its unreasonable offers and unjustified pressure to hastily reach an agreement, show that US isn't interested in a strong deal that would satisfy both parties," he added.
US approach to Iran's principled demands, coupled with its unreasonable offers and unjustified pressure to hastily reach an agreement, show that US isn't interested in a strong deal that would satisfy both parties. Absent US political decision, the talks get knottier by the hour.— علی شمخانی (@alishamkhani_ir) March 10, 2022
Ukraine shadow on Iran deal
The United States reaffirmed its position that a deal remained close and could even be reached "in the coming days."
"It's really down to a very small number of outstanding issues," State Department spokesman Ned Price said at a news conference on Thursday, without mentioning any new demands from Washington.
"But the reason these particular issues are outstanding is that they are among the most difficult ones."
Moscow has said it wants written assurances from Washington that sanctions imposed on it over the Ukraine attack will not affect its economic and military cooperation with Tehran.
The negotiations to revive the deal involve Iran as well as France, Germany, Britain, Russia and China directly, and the United States indirectly.
Washington's unilateral withdrawal from the accord and its reimposition of biting economic sanctions prompted Iran to begin rolling back on its own commitments.
The United States has described Russia's new demands as "irrelevant", while France warned they could dash hopes for a revived nuclear accord.