In his letter to the Congress on Wednesday, US Secretary of State Rex Tillerson, acknowledged that Iran was compliant to the accord, but blasted the country as "the world's leading state sponsor of terrorism."
Tillerson claimed that Tehran has been fueling various military conflicts in the Middle East, undermining US interests in countries such as Syria, Yemen, Iraq and Lebanon.
It was the first time that the Congress was informed on how Iran was fulfilling its obligations under the Joint Comprehensive Plan of Action (JCPOA), usually referred to as the Iran nuclear deal, under the Trump administration. The State Department must update US senators on the issue every 90 days.
Comment: Tillerson on Trump's review order: 'Iran complies with nuclear deal but sponsors terrorism'
Zarif took to Twitter to respond to Tillerson's claims, stressing that Washington should "fulfill its own commitments" as part of the deal.
"Worn-out US accusations can't mask its admission of Iran's compliance w/ JCPOA," the Foreign Minister added as cited by Reuters.
Moscow commented on Tillerson's claim by saying that secretary of state should have separated the allegations of terrorism and the nuclear deal as they "have nothing in common," according to Mikhail Ulyanov, the head of the Russian Foreign Ministry's Department for Non-Proliferation and Arms Control.
"If the deal does not work, then specific complaints should be made regarding its functioning. The Americans can't do this. The IAEA [International Atomic Energy Agency], an independent participant in this process, confirms that the Iranians are implementing everything. Therefore, any claims are irrelevant here, it seems to me," Ulyanov said.
Washington blames Tehran for supporting various groups that it views as terrorist organizations, including Lebanese Hezbollah, Palestinian Hamas and the Houthis in Yemen.
Iran has also been backing the Syrian government of President Bashar Assad, also sending military advisers and fighters to Iraq to help fight Islamic State (IS, formerly ISIS/ISIL) there.
The Iranian nuclear deal, which took years to negotiate, restricted the nuclear ambitions of Tehran in exchange for lifting financial and oil sanctions.
The accord signed between Iran and the P5+1 (China, France, Russia, United Kingdom, the US, plus Germany) and the EU was touted as one of the main foreign policy achievements of the Obama administration.
However, Donald Trump called it "the worst deal ever negotiated" during his campaign for the White House.
A special inter-agency review of policy towards Iran will now look into if the lifting of sanctions against Tehran was in the interest of the US.