Disappointment over their continued economic stagnation has created an opening for conservative candidates in May 19 elections who are opposed to Iranian President Hassan Rouhani, a relative moderate who helped oversee the nuclear deal's conclusion.
US Secretary of State Rex Tillerson said this week in a letter that Iran was fulfilling its commitments but warned that the White House was reviewing the agreement.
In a statement on Wednesday, Mr Tillerson said a review, which he had announced in a letter to Congress a day earlier, would look at the whole U.S. policy towards Iran - taking in not only Tehran's compliance with the nuclear deal but also its actions in the Middle East.
Tillerson was free to inform Congress that he could not certify that Iran was in compliance, or to even ignore the deadline all together and kick off the process of withdrawing from the multilateral executive agreement.
The US admitted this week that Iran has stuck to its side of the bargain, but Secretary of State Rex Tillerson said it would not stop Iran becoming a nuclear-armed state, and Washington officials regularly accuse Iran of fomenting unrest in the Middle East and sponsoring terrorism.
In spoken remarks, though, he talked only of Iran's bad behaviour and linked that to the future of the deal.
At the same time, analysts say, Iranian hard-liners believe that the U.S.is unlikely to withdraw from the deal and risk a diplomatic crisis with the five other signatories - Britain, China, France, Germany and Russian Federation. On the one hand, Trump wants to show he's being tougher than Obama toward Iran, but on the other hand, he's not yet ready to rip up the deal.More news: Assad allies say US attack on Syria air base crosses 'red lines'
"Iran spends its treasure and time disrupting peace", Tillerson said.
The administration says it is reviewing these accords and could still pull out of them.
Iranian hardliners have regularly criticised Zarif and President Hassan Rouhani for their role in negotiating the 2015 nuclear deal, which they see as capitulation to Western powers.
"Every administration, when it doesn't know what the hell to do, reviews things", Slavin said.
"The worn-out allegations by the U.S. can not cover the country's admission of Iran's implementation of its nuclear deal undertakings", Zarif said.
Republicans in the US Congress have also been critical, advocating new sanctions on Iran for supporting terrorism and for its ballistic missile program. But they refuse to express concern.