President Donald Trump on Tuesday reimposed a naval blockade of all Iranian ports and threatened to hit power plants and bridges next week unless Tehran resumes negotiations, in the latest US escalation of the conflict.The US also began a fresh round of strikes "to continue degrading Iranian capabilities used to attack commercial shipping in the Strait of Hormuz," the US military said.

Tehran says it has again closed the strait after hostilities between Iran and the US reignited last week, fraying an already fragile truce reached in June after several months of fighting that has killed thousands.

"I'll save the energy targets for last, but ultimately we'll hit energy targets," Trump said in an interview with Fox News’ Trey Yingst.

"Next week comes the power plants, next week comes the bridges," Trump said, "unless they get to the table and negotiate."

The 1949 Geneva Conventions on humanitarian conduct in war prohibit attacks on sites considered essential for civilians.