"It shouldn't have been signed".
Tillerson accused Iran of "alarming ongoing provocations" to destabilise countries in the Middle East and said the Trump administration had launched a review of its policy towards Tehran that will include the 2015 nuclear deal.
Trump's administration is demanding that Congress fund a bigger US border wall with Mexico and is suggesting that his administration could scrap the USA nuclear deal with Iran.
At a joint news conference on Thursday, he said Iran was failing to fulfill the "spirit" of its nuclear deal with world powers and that the 2015 agreement shouldn't have been signed.
Tillerson spoke a day after certifying to Congress that Iran is complying with its obligations under the 2015 deal, a requirement for Tehran to continue receiving relief from nuclear sanctions.
Trump's criticism came two days after the US certified that Iran was complying with the deal, which was negotiated during President Barack Obama's presidency.
However, Donald Trump called it "the worst deal ever negotiated" during his campaign for the White House. Under the groundbreaking agreement brokered by the Obama administration and allies, the USA and other European and western countries lifted sanctions against Iran in exchange for the Shia state opening up its nuclear sites to inspectors and dismantling centrifuges which the Obama administration claimed will prevent Iran from acquiring a nuclear weapon. "We're analysing it very, very carefully and will have something to say about it in the not-too-distant future".
Foreign Minister Mohammad Javad Zarif wrote on Twitter that "worn-out United States accusations can't mask its admission of Iran's compliance" with the nuclear deal.More news: Queen Elizabeth II turns 91 with day at the horse races
Obama considered the nuclear agreement one of his most important foreign-policy achievements, saying it would end the threat that Iran would have a nuclear weapon.
The state department is obliged to inform Congress every 90 days about Iran's compliance with the deal.
WASHINGTON (AP) - Iran is failing to fulfill the "spirit" of its nuclear deal with world powers, President Donald Trump has declared, setting an ominous tone for his forthcoming decision about whether to pull the US out of the landmark agreement.
Under the JCPOA, Iran undertook to put limitations on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against the country.
"This deal represents the same failed approach of the past", Tillerson said at a hastily arranged press conference on Wednesday.
"For decades, they have committed terrorist acts across the region", Haley said, adding that Iran has worked with allied Lebanese Hizballah militias to stir conflict. Tillerson said that there is enough evidence to prove that Iran's provocative actions are a threat to the United States and the entire world.
She said the review was a fig leaf to cover a decision by the Trump administration to abide by the Iran accord, if grudgingly. Trump's National Security Council (NSC) now is evaluating whether Iran - as it maintains it has - is in compliance with the 2015 nuclear deal, and if the United States can impose sanctions.