US working with partners to get Iran change its behaviour: White House

White House Deputy Press Secretary Hogan Gidley's remarks came amidst an unconfirmed report in an Australian media outlet saying the US was preparing to launch a strike on Iran.

"I can't confirm that report. I'd refer you to DOD (department of defense) on that matter. What I can tell you is the President has been very clear about where he stands on Iran," Gidley told reporters abroad Air Force One yesterday.

Trump warned Hassan Rouhani on Monday that Tehran risked "consequences the likes of which few throughout history have suffered before" if he threatened the US again, hours after the Iranian President cautioned that America's hostile threats may trigger "the mother of all wars."

Rouhani had also warned Trump to stop "playing with the lion's tail" and threatening Iran, "or else you will regret it".

Trump in May pulled the US out of the 2015 Iran nuclear agreement struck by the Obama administration by calling it the "the worst" deal ever negotiated.

"Their actions - their destabilisation of the region, their desire and efforts to obtain a nuclear weapon - it's one of the reasons that he called the Iran deal the worst deal he'd ever seen, the worst deal in history, and why he got out of it," Gidley said.

"We know that the Iran deal did not prevent a pathway to prevent Iran from obtaining a nuclear weapon; it actually paved it. But we're working with our partners and allies to try and get Iran to change its behaviour and stop its action across the region. And we're working with Israel to do the same thing," he said in response to a question.

Trump has alleged that the nuclear deal did not restrict Iran's "destabilising activities" in the region enough, and could not detect or prevent any breaking of its terms.

The agreement forced Iran to curtail its uranium enrichment capacity to prevent it developing nuclear weapons, and imposed stringent verification processes, in exchange for relief on crippling sanctions.

Iran insists its nuclear programme is entirely peaceful, and its compliance with the deal has been verified by the International Atomic Energy Agency (IAEA), which has said Iran is honouring its commitments.

Earlier, US Secretary of State Mike Pompeo had said he wanted to try to stop countries importing Iranian oil by November as part of stepping up pressure on Tehran.

The US Treasury has said there will be wind-down periods of 90 and 180 days before sanctions are implemented.

The first deadline, on August 6, will affect the purchase of US dollars, trade in gold and certain other metals, as well as aviation and the car industry.

The next, on November 4, will target Iran's financial and oil institutions.

Iran is one of the world's largest oil producers, with exports worth billions of dollars each year.