US President Donald Trump threatened to target Iran's energy infrastructure and bridges if Tehran refuses to return to negotiations, saying military operations around the Strait of Hormuz will continue until he decides they should stop.

US President Donald Trump warned that Washington would intensify its military campaign if Iran does not return to the negotiating table.

Speaking to Fox News, Trump said US forces were continuing strikes against Iranian targets along the country's coastline.

He said the attacks would escalate unless Tehran agreed to negotiations.

"We will hit them very hard tonight, tomorrow night and the night after," Trump said.

"If they don't come to the table, we will destroy all of their power plants and all of their bridges," he added.

Trump also defended continued military operations around the Strait of Hormuz, arguing that the strategic waterway must remain open for international shipping.

He said the attacks in and around the strait would continue "until I say enough."

Trump further claimed that US forces had struck Kharg Island, one of Iran's main oil export terminals in the Persian Gulf, on two occasions.

He added that he would consider seizing the island if Iranian forces could be pushed back sufficiently.

Trump has previously made similar threats against Iran's energy infrastructure, remarks that have drawn criticism from legal experts, who argue that deliberate attacks on civilian infrastructure could violate international humanitarian law. (ILKHA)