"I'm hearing little stories about Iran," Trump told reporters as he hosted Hungarian Prime Minister Viktor Orban at the White House.

"If they do anything, it would be a very bad mistake," Trump warned. "If they do anything they will suffer greatly."

The US has ramped up pressure on Iran in recent days, accusing Tehran of planning "imminent" attacks and bolstering the American military presence in the Gulf.

The spike in tensions comes a week after Iran announced it was suspending some of its commitments under the 2015 nuclear agreement, one year after Trump withdrew from the accord and slapped tough sanctions on the Islamic republic.

US Secretary of State Mike Pompeo scrapped an expected Moscow trip on Monday, heading instead to Brussels to discuss the crisis with his counterparts from Britain, France and Germany.

Trump last week declared himself open to talks with the Iranian leadership, a position reiterated on Monday by Brian Hook, the US special envoy for Iran.

"We believe that Iran should try talks instead of threats. They have chosen poorly by focusing on threats," Hook told reporters.