President Hassan Rouhani pledged to resist the US recent move to impose a fresh raft of sanctions, which he condemned as contravention of the 2015 nuclear deal.
"The Americans have been seeking excuses to impose new sanctions. It is against the spirit and letter of the JCPOA," the president said, referring to the pact by its formal title, the Joint Comprehensive Plan of Action.
It was concluded in July 2015 between Iran and six powers, namely the US, Britain, France, China and Russia plus Germany, and went into force six months later to give Iran relief from international sanctions in return for curtailing its nuclear program.
"We will not overlook the US violations [of the accord] and will resist them," Rouhani told a Cabinet meeting on Wednesday, IRNA reported.
The US State Department released a statement on Tuesday to announce the new penalties over Iran's ballistic missile program and alleged "malign activities" in the region.
They targeted 18 entities and individuals for supporting what the statement alleged were "illicit Iranian actors or transnational criminal activity".
The statement cited Tehran's support for anti-Israel resistance groups and the government of Syrian President Bashar al-Assad.
Rouhani said Iran will stay vigilant not to fall into a US trap meant to provoke the Islamic Republic to walk away from the action plan.
"The Islamic Republic always has and will honor its commitments. Today one of the ploys of the Americans is to act in a way to make Iran say it is abandoning its obligations … This plot is doomed," he said.
The news of the new sanctions came two days after the six-month-old administration of US President Donald Trump confirmed for the second time that Iran was complying with the nuclear agreement.
Iran's Foreign Ministry denounced the sanctions move as "contemptible and worthless".
Foreign Minister Mohammad Javad Zarif told CBS News the sanctions "poison the atmosphere" and breach JCPOA's "spirit".
"We will look at it and see whether it violates the letter of the deal. And we will act accordingly," he said.
Trump is critical of the action plan, negotiated under his predecessor Barack Obama, and has branded it "the worst deal ever".
The JCPOA partners of the United States have all expressed support for the continued implementation of the international agreement and have resisted Trump's call for a full review.
