U.S. Secretary of State Rex Tillerson on Wednesday accused Iran of "alarming ongoing provocations" to destabilise countries in the Middle East and of undermining U.S. interests in Syria, Iraq and Lebanon.

In a letter to US House of Representatives Speaker Paul Ryan released late on Tuesday, Tillerson declared that Iran was meeting its commitments under the 2015 nuclear deal but there were concerns about Tehran's role as a state sponsor of terrorism. Tillerson's comments come after he announced an inter-agency review of whether the suspension of Iran sanctions under the 2015 agreement is in the interest of American national security.

"Secretary Tillerson made clear that regardless of Iran's technical compliance with the nuclear deal, the administration is under no illusion about the continued threat from Teheran and is prepared to work closely with Congress to push back", Corker said in a statement on Wednesday.

When Spicer was questioned whether Trump was concerned Iran was cheating on the deal, he said "That's why he's asking for this review".

The nuclear agreement, negotiated during Barack Obama's presidency, placed limitations on Iran's nuclear programme in exchange for lifting economic sanctions against Iran.

But the top United States diplomat stopped short of threatening to jettison the 2015 agreement that was brokered by world powers, or say whether the Trump administration would punish Iran with new sanctions.

The nuclear deal was reached in Vienna in July 2015 between Iran and Britain, China, France, Germany, Russia and the United States.

Critics of the agreement, including Israel, have argued that when some of the terms of the deal expire in 10 and 15 years it will leave Tehran on the threshold of building a bomb.

The diplomat said the intensified language is also a shot across the bow by the USA to Iran to warn: "Just because North Korea is misbehaving, it doesn't mean we aren't still watching you". James Mattis, Trump's secretary of defense, expressed support for abiding by the Iran nuclear deal in his confirmation hearings.

"An unchecked Iran has the potential to travel the same path as North Korea - and to take the world along with it, " Tillerson said.

"The evidence is clear - Iran's provocative actions threaten the United States, the region and the world", Tillerson said.

However, the USA admits that Tehran is complying with the 2015 agreement.

She said the review was a fig leaf to cover a decision by the Trump administration to abide by the Iran accord, if grudgingly.

Instead, the Trump administration would conduct a "comprehensive review" of USA policy toward Iran, Tillerson said, leaving one of Barack Obama's signature policies in place - for now.

Illustrative: Iran's heavy water nuclear facilities near the central city of Arak.

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.

Trump's spokesman Sean Spicer said the review would be conducted by USA government agencies over the next 90 days and recommendations would be presented to the president as to whether to stick by the deal.