The push for new sanctions appears to have gained new life amid the recent wave of anti-regime protests in Iran and more specifically the Iranian government's harsh crackdown on demonstrators last week.
Such measures, said Mr. Zarate, "would be consistent with the agreement's allowance for the application of non-nuclear sanctions". "You either waive the sanctions or you don't and if you don't you're in breach", an anonymous official said.
The European signatories of the Iran nuclear deal have warned Donald Trump from ditching the accord, arguing that it is essential to maintain worldwide security and is achieving its goals.
Under the agreement, Iran has agreed to dramatically reduce its stockpile of enriched uranium and cut the number of gas centrifuges it operates to produce the nuclear ingredient, with strict limits on other nuclear technologies like heavy water.
In defiance of Mr Trump's efforts to withdraw Washington's involvement, the Europeans have sought to cast the battle to save the deal as important to the principle of non-proliferation.
The deal struck in 2015 between seven world powers - the U.S., UK, Iran, Russia, France, China, and Germany - was one of the signature foreign policy achievements of Barack Obama's presidency. "IAEA has verified Iran's full compliance, but continuation will depend on full U.S. compliance", he wrote. European countries are banking on the deal, as many began investing in Iran after the sanctions were lifted.
Mogherini, who played an important role in crafting the nuclear accord, has vowed to preserve the deal and has lobbied USA lawmakers in Washington. But some liberal Democrats who support the deal want to pass legislation that would make it harder for Trump to pull Washington out without congressional consent.
The International Atomic Energy Agency (IAEA) has repeatedly said Iran is keeping up its side of the agreement, most recently in November. He called the agreement a "considerable diplomatic accomplishment".
"I don't think that anybody has produced a better alternative to the JCPOA as a way of preventing the Iranians from going ahead with the acquisition of a military nuclear capability", he said.
Don't Iran's threats prove the deal's critics' point that the sunset clause, permitting Iran to continue experiments with advanced centrifuges, and having Iran disassemble instead of destroy its thousands of centrifuges means that Iran will be able to walk out to a nuclear weapon at the end of the deal?
"We know that it's absolutely necessary to have the signal that it's possible, by diplomatic approaches, to prevent the development of nuclear weapons in a time where other parts of the world are discussing how to get nuclear weapons", he told reporters in Brussels.
Trump in October chose not to certify that Tehran is complying with the deal and warned he might ultimately terminate it.
Kamalvandi said, "If suspension of the sanctions will not be extended, Iran will take the first retaliatory action immediately".