Donald Trump intensified pressure on Iran on Sunday, warning that the United States could strike key Iranian infrastructure if Tehran fails to reopen the Strait of Hormuz before Tuesday, when Washington’s 48-hour ultimatum expires.

In a post on Truth Social, Trump said that “Tuesday will be Power Plant Day and Bridge Day, all in one, in Iran,” signaling potential attacks on Iranian electrical facilities and bridges.

Trump again demanded that Iran reopen the “damn strait” of Hormuz, through which roughly one-fifth of the world’s oil supply passes. The closure of the waterway has become one of the most destabilizing consequences of the conflict that began on February 28, after U.S. and Israeli strikes on Iran.

Strait of Hormuz is regarded as one of the world’s most critical energy chokepoints. Analysts warn that any U.S. strike on Iranian infrastructure could push oil prices, fuel costs and global supply chains even higher.

Trump had already warned on Saturday that Iran had “48 hours before all hell breaks loose” unless the strait was reopened. The deadline expires Monday at 8:00 p.m. Washington time, midnight GMT Tuesday.

The renewed threat came alongside a striking admission by the U.S. president. In an interview with Fox News, Trump acknowledged for the first time that the United States had sent weapons to anti-government protesters in Iran during demonstrations held in January.

“We sent them a lot of weapons. We sent them through the Kurds,” Trump said, adding that he believed some of the weapons remained in Kurdish hands.

The January protests in Iran were driven by the country’s economic crisis and widespread anger at the ruling clerical regime. Opposition groups reported thousands of deaths and tens of thousands of arrests following the crackdown. Trump’s admission is likely to further heighten tensions between Washington and Tehran.