President Donald Trump warned that the United States was "not finished" attacking Iran as strikes continued Tuesday, as Tehran broadened its offensive against Gulf states after its Houthi allies threatened to blockade Saudi ports.

Two weeks after fighting resumed between the decades-old foes, Trump said Iran would need more than 20 years to recover from the damage inflicted in the Middle East war.

"If we left right now, it would take Iran 20, 25 years to rebuild," he said. "We're not finished at all...we're not leaving right now."

The US military said it had completed an 11th consecutive night of strikes against Iran, saying it targeted military infrastructure to "further degrade Iran's ability to threaten commercial shipping in the Strait of Hormuz.