TEHRAN (Press Shia) – US President Donald Trump said he is willing to meet with Iran's leadership, without preconditions, "whenever they want," a sharp departure from his threats against the Islamic Republic last week.

"I would certainly meet with Iran if they wanted to meet," Trump said during a joint news conference at the White House alongside Italian Prime Minister Giuseppe Conte on Monday, CNN reported.

"I do believe that they will probably end up wanting to meet. I'm ready to meet whenever they want to,” he added.

"No preconditions," he added. "They want to meet, I'll meet, whenever they want."

Monday's olive branch from Trump marks an abrupt shift in tone, and may be little more than theater with US midterm elections looming on the horizon.

The US President has been a strident critic of Iran, threatening Tehran with "consequences" as recently as July 22, while his administration pursues a strategy that many see as regime change in all but name.

Trump and his senior officials have ramped up the rhetoric against Tehran, promising to "crush" its economy with sanctions and accusing it of fomenting “terrorism and regional instability”.

Trump touted the benefits of diplomacy, saying he would "meet with anybody" and once again argued that his July 12 meeting with Russian President Vladimir Putin — which drew heated bipartisan criticism — was a success.

"Speaking to other people, especially when you're talking about potentials of war and death and famine and lots of other things — you meet. There's nothing wrong with meeting," Trump said.

While Trump said he would apply no preconditions to meeting with Iran, he did appear to hedge the possibility of a meeting on an ability to "work something out that's meaningful."

US Secretary of State Mike Pompeo said Trump had made the offer before. "The President wants to meet with folks to solve problems," Pompeo told CNBC.

"If the Iranians demonstrate a commitment to make fundamental changes in how they treat their own people, reduce their malign behavior, can agree that it's worthwhile to enter into a nuclear agreement that actually prevents proliferation, then the president said he's prepared to sit down and have the conversation with them,” he claimed.