US President Donald Trump has warned that the United States will target Iran's bridges and power plants next week unless Tehran returns to the negotiating table.

The remarks were made during an interview with Fox News and aired as the United States and Iran exchanged fire for the fourth consecutive day, The Caspian Post reports via BBC.

Earlier, Trump reversed his proposal to impose a 20% fee on cargo vessels transiting the Strait of Hormuz but resumed a blockade of Iranian ports.

"Next week it gets really bad for them," Trump said. "We're going to knock out all their power plants. We're going to knock out all their bridges unless they get to the table and negotiate."

Trump had previously threatened in April to bomb Iranian civilian infrastructure, including bridges and power plants.

At the time, UN High Commissioner for Human Rights Volker Türk responded by stating: "Under international law, deliberately attacking civilians and civilian infrastructure is a war crime."

The 1949 Geneva Conventions governing humanitarian conduct during war prohibit attacks on infrastructure considered essential for civilian populations.

"I'll save the energy targets for last, but ultimately we'll hit energy targets," Trump said in an interview on Special Report with Bret Baier.

He said US negotiators had conveyed to their Iranian counterparts that they "'better make a deal, or you're not going to have anything left'".

The escalation in rhetoric comes after Trump said a 20% toll he had threatened to impose in the Strait of Hormuz would be replaced by "massive" trade and investment deals with Gulf states. His announcement came hours before the US resumed its blockade of Iranian ports.

Renewed strikes between the US and Iran triggered a sharp rise in oil prices as tanker traffic through the Strait has virtually stalled.

US Central Command (CENTCOM) said that its "forces began launching an additional round of strikes against Iran to continue degrading Iranian capabilities used to attack commercial shipping" in the key waterway.