ARAD, Israel — Iran and the allied Lebanese militant group Hezbollah stepped up attacks on Israel on Sunday as the United States and Iran threatened to target critical infrastructure in the war in the Middle East, now in its fourth week.

Iran said the Strait of Hormuz, crucial to oil and other exports, would be “completely closed” immediately if the U.S. follows up on President Donald Trump ‘s new threat to attack its power plants. Trump late Saturday set a 48-hour deadline to open the strait. Iran’s parliament speaker said Tehran also would retaliate against U.S. and Israeli energy and wider infrastructure.

Israeli leaders visited one of two southern communities near a secretive nuclear research site struck by Iranian missiles late Saturday, with scores of people wounded. Prime Minister Benjamin Netanyahu said it was a “miracle” no one was killed.

He also claimed Israel and the U.S. were well on their way to achieving their war goals and asked the world for more support. The aims have ranged from weakening Iran’s nuclear program, missile program and support for armed proxies to enabling the Iranian people to overthrow the theocracy.

The developments signaled the war, which the U.S. and Israel launched Feb. 28, was moving in a dangerous new direction, despite Trump’s comment last week he was considering “winding down” operations. It has killed over 2,000 people, rattled the global economy and sent oil prices surging.

Hezbollah claimed responsibility for an airstrike that killed a man in northern Israel, while Lebanese President Joseph Aoun called Israel’s targeting of bridges in the south “a prelude to a ground invasion.”

Energy and desalination plants are threatened: Iran has practically closed the Strait of Hormuz that connects the Persian Gulf to the rest of the world. Roughly one-fifth of global oil supply passes through it, but attacks on ships and threats of further strikes have stopped nearly all tanker traffic. Some of the largest oil producers have made cuts because their crude has nowhere to go.

The U.S. and its allies in Europe and Asia rely heavily on the oil to meet energy demand. In its most recent attempt to relieve pressure on energy prices, the U.S. has lifted some sanctions on Iranian oil at sea.

Trump said if Iran didn’t open the strait, the U.S. would destroy its “various POWER PLANTS, STARTING WITH THE BIGGEST ONE FIRST!”

The U.S. has argued that Iran’s Revolutionary Guard controls much of the country’s infrastructure and uses it to power the war effort.

Iranian parliament speaker Mohammad Bagher Qalibaf responded on X that if Iran’s power plants and infrastructure are targeted, then vital infrastructure across the region — including energy and desalination facilities — would be considered legitimate targets and “irreversibly destroyed.”

Under international law, power plants that benefit civilians can be targeted only if the military advantage outweighs the suffering it causes to civilians, legal scholars say.

Separately, Iranian officials said they would keep providing safe passage through the strait to vessels from countries other than its enemies.

Strikes in Israel and Iran bring new nuclear concerns: Iran said its strikes in the Negev Desert late Saturday were in retaliation for an earlier attack on Iran’s main nuclear enrichment site in Natanz, according to state-run media.

Tehran praised the attack as a show of strength, even as Israel’s military asserts that Iranian missile launches have gradually decreased in frequency since the war began.

“If the Israeli regime is unable to intercept missiles in the heavily protected Dimona area, it is, operationally, a sign of entering a new phase of the battle,” Qalibaf said.