"This deal represents the same failed approach of the past", Tillerson said at a hastily arranged press conference on Wednesday.
Tillerson said one of the mistakes in the way the agreement was put together was that it ignored all the other serious threats Iran posed outside of its nuclear programme.
Iran also "maintains a long-standing hostility towards Israel, providing weapons, training and funding to Hamas and other Palestinian terrorist organizations", said the secretary of state, citing reports that Iran displayed a missile inscribed "death to Israel" during a military parade on Tuesday.
Under the worldwide agreement, Iran is allowed to enrich and store some uranium for energy production, although it had to reduce its uranium stockpile by 96 percent, idle many of its enrichment centrifuges and pour concrete into its heavy-water nuclear reactor.
Kiyaei noted that harsher rhetoric from the Trump administration, actions like the travel ban on several Muslim-majority countries including Iran, and a disengagement from limited direct communications has already deteriorated U.S.
Pence visited Seoul, South Korea, this week to declare that the United States was united with its allies to stem North Korea's threat. But he told Congress in a letter that the Trump administration was reviewing the lifting of US sanctions against Iran to determine if that was in USA interests.
Reiterating the charge yesterday, Tillerson said Iran's provocative actions threaten the United States, the region and the world.
"It is another example of buying off a power who has nuclear ambitions", Tillerson said of the 2015 Joint Comprehensive Action Plan to restrict Iran's nuclear power.
The enigmatic remarks left top Republicans on Capitol Hill nonplused.
Senator Bob Corker, chairman of the Senate Foreign Relations Committee, said the Trump administration appeared to be preparing a tougher line against Iran.
The agreement came into force on January 16, 2016, after the International Atomic Energy Agency (IAEA) submitted a report confirming the readiness of Iran's authorities to implement the program to reduce the country's nuclear potential. USA sanctions, as approved by Congress, were suspended instead of revoked; they can be reimposed with the stroke of a presidential pen.
The other countries that were part of the deal - Britain, France, Germany, Russia and China, along with the European Union - remain supportive of the pact and would likely object to any re-imposition of American sanctions. Trump faces a mid-May deadline, as imposed by Congress, to decide whether to continue the suspension of sanctions.
In their first congratulatory phone calls to Trump after his electoral victory, both President Vladimir Putin of Russian Federation and Chancellor Angela Merkel of Germany stressed the need to keep the Iran deal in place.
For Trump, the nuclear agreement will pose an early test between the pull of his campaign statements and the push of political realities.
Never, ever, ever in my life have I seen any transaction so incompetently negotiated as our deal with Iran.
Administration officials have made clear in recent days that they are very focused on Iran. CBS News Chief White House Correspond...