Tillerson made the remarks on Wednesday after he and Iranian Foreign Minister Mohammad Javad Zarif met as parties to the Joint Comprehensive Plan of Action (JCPOA) at an EU-organized event on the sidelines of the UN General Assembly in New York where EU foreign policy chief Federica Mogherini said that all parties to the nuclear deal agree that Iran is in compliance with the plan.
Tillerson told reporters after the meeting that the United States did not dispute that Iran was in "technical compliance" with the JCPOA, saying that Mogherini's comments referred only to technical compliance with the nuclear deal.
He said that the US complaints about Iran are political in nature, without elaborating what he means with these comments.
"I think the high commissioner was reflecting the rigid and strict contours of the agreement itself," he said.
Commenting on the meeting of the parties to the nuclear deal, Tillerson said, "It was not a technical discussion, it was a political discussion of the political aspects.”
"So we had a very open and candid exchange between all of the parties to that agreement," he added, calling the meeting "useful" but inconclusive.
Tillerson also said he told Zarif that Washington continues to have "significant issues" with the nuclear deal.
"It was a good opportunity to meet, shake hands. The tone was very matter of fact. There was no yelling, we didn't throw shoes at one another," he said.
"It was not an angry tone at all. It was a very, very matter of fact exchange about how we see this agreement very differently,” he added.
Tillerson pointed out that US President Donald Trump particularly is opposed to the so-called "sunset clause" in the nuclear accord, which sees the restrictions on Iran's nuclear enrichment lifted after 2025.
During a speech before the UN General Assembly on Tuesday, Trump railed against the Iran nuclear deal, saying it is "one of the worst and most one-sided transactions the United States has ever entered into,” a characterization he often used during his presidential campaign.
“I don’t think you’ve heard the last of it, believe me,” Trump said.
The Trump administration has desperately sought a pretext to scrap or weaken the 2015 deal and get rid of the limits the deal imposes on the US ability to pursue more hostile policies against Iran.
However, Washington’s European allies seek to prevent the collapse of the deal and are stepping up efforts to convince Trump not to abandon the accord.
Trump is nearing an October 15 deadline for certifying Iran's compliance with the JCPOA, which puts limitations on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against Tehran.
The International Atomic Energy Agency (IAEA) has on multiple occasions affirmed Iran's adherence to its commitments under the nuclear agreement.