United States President Donald Trump on Saturday gave Iran a 48-hour ultimatum, warning that the U.S would target its power plants if the Strait of Hormuz is not reopened.

“If Iran doesn’t FULLY OPEN, WITHOUT THREAT, the Strait of Hormuz, within 48 HOURS from this exact point in time, the United States of America will hit and obliterate their various POWER PLANTS, STARTING WITH THE BIGGEST ONE FIRST!” Trump said in a post on Truth Social.

The president’s warning marks a significant escalation in rhetoric amid rising tensions over the strategically important waterway.

Traffic through the Strait of Hormuz—a critical chokepoint for global oil and gas shipments that carries about one-fifth of the world’s crude supply, has been largely restricted since early March, shortly after the conflict with Iran began.

Trump’s remarks followed his comments to reporters on Friday, where he described reopening the strait as a “simple military maneuver.”

“It’s relatively safe, but you need a lot of help in the sense of you need ships, you need volume,” he said.