US Secretary of State Rex Tillerson has accused Iran of “alarming ongoing provocations” aimed at destabilising the Middle East and undermining America’s interests in the region.
“An unchecked Iran has the potential to travel the same path as North Korea and to take the world along with it,” Mr Tillerson said.
President Donald Trump earlier ordered a review of the Iran nuclear deal.
However, the US admits that Tehran is complying with the 2015 agreement.
Iran has so far made no public comments on the latest developments.
Iran has repeatedly denied accusations by the West that it was ever trying to develop nuclear weapons.
On Tuesday, Washington accused North Korea of trying to “provoke something”, after Pyongyang conducted a failed missile test over the weekend.
In response, North Korea said it may test missiles on a weekly basis, and warned of “all-out war” if the US takes military action.
‘Many threats’
Speaking on Wednesday, Mr Tillerson said the Iran review, which he announced in a letter to Congress a day earlier, would not only look at Tehran’s compliance with the nuclear deal but also its actions in the Middle East.
Mr Tillerson accused Iran of undermining US interests in Lebanon, Iraq, Syria and Yemen.
“A comprehensive Iran policy requires we address all of the threats posed by Iran, and it is clear there are many,” he said.
Raising stakes: Analysis by BBC State Department correspondent Barbara Plett Usher
In announcing a broad review of Iran policy the Trump administration has not jettisoned the nuclear deal.
But Rex Tillerson has come pretty close to saying the agreement is not worth keeping, even though he’s had to admit it’s working.
This week the secretary of state informed congress that Tehran is keeping its side of the bargain to restrict its nuclear programme in exchange for the lifting of sanctions, which he’s required to confirm every 90 days.
In spoken remarks, though, he talked only of Iran’s bad behaviour and linked that to the future of the deal – a message that will resonate far more on Capitol Hill and to which it was probably aimed.
Former President Barack Obama would have agreed with all the charges: that Iran is a state sponsor of terrorism, that it supports proxies which undermine US interests in the region, that it’s hostile to Israel and that its ballistic missile tests challenge UN Security Council prohibitions.
But Mr Obama kept those issues separate from the nuclear agreement, which would have been impossible to achieve without that narrow focus.
Mr Tillerson, on the other hand, called this a mistaken approach and said the review would take a comprehensive look at all of the threats posed by Iran.
The secretary of state earlier acknowledged the Iranians had met the terms of the 2015 deal, but raised concerns about the country as a “state sponsor of terrorism”.
President Trump has described the landmark agreement as the “worst deal ever”.
However, his predecessor Barack Obama argued the deal, between Iran and six world powers including China, Russia and the UK, was the best way to prevent Iran getting a nuclear weapon.
Sanctions were lifted after the International Atomic Energy Agency (IAEA) certified Tehran had restricted its sensitive nuclear activities.
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