Days of back-and-forth strikes by the U.S. and Iran across the Middle East — and renewed threats to the waterway crucial to global energy supplies — have shredded the interim deal to end the conflict and the region could tip back into all-out war.

The U.S. first imposed a blockade in April and then lifted it last month after signing the interim deal that paused the fighting and set a 60-day period for negotiations over issues such as Iran’s nuclear program. Those talks have stalled as fighting over the Strait of Hormuz has intensified.

When the U.S. and Israel launched the war on Iran on Feb. 28, Tehran effectively closed the waterway to shipping traffic — a move that sent the price of oil, fertilizer and many other goods soaring far beyond the region and gave Iran major leverage in negotiations. Those rising prices pose a particular challenge to U.S. President Donald Trump and his Republican Party, which hopes to retain control of Congress in elections in November. But Washington has struggled to successfully reopen the waterway.

Iran’s paramilitary Revolutionary Guard threatened Wednesday to halt all energy exports from the Middle East over the blockade.

“The export of oil and gas from the region will be either for everyone or for no one,” it said.

Both the US and Iran launch attacks as the blockade is reimposed

The U.S. carried out a wave of strikes, hitting dozens of targets overnight, the military’s Central Command said Wednesday, and then resumed striking Iran during daylight — an unusual move that further signaled the increasing tempo of the attacks.

Within 17 hours of reimposing the blockade on Iranian ports, Central Command said U.S. forces had “redirected” two commercial vessels attempting to run the blockade.

“The U.S. military remains vigilant and prepared to ensure full compliance,” it said on social media.

Among the U.S. military’s targets was Greater Tunb Island, which is viewed as a strategic point in the Strait of Hormuz. Central Command said the attack targeted Iranian defense and missile sites.

Iran took control of three islands — Abu Musa, Greater Tunb and Lesser Tunb — from what would become the United Arab Emirates in 1971. The UAE has sought to reclaim them.

Some analysts have suggested that if the U.S. seized the islands, they could allow it to control the strait.

Another strike targeted a barracks for Iran’s 388th Mechanized Infantry Brigade, which operates tanks and armored vehicles, in Sistan and Baluchestan province, Iranian state television reported. The report said the Americans fired at least 13 missiles in the attack and that the seven dead included conscripts and career soldiers. A number of troops were wounded.

Including those at the barracks, more than 30 people have been killed in recent days, Iranian government spokesperson Fatemeh Mohajerani said, without elaborating.

Hossein Kermanpour, a spokesperson for the Health Ministry, meanwhile, said over 260 people were wounded in overnight strikes alone — a figure far larger than for any other round of recent violence between Iran and the U.S. He did not say how many people were killed overnight.

The army said it would make “a decisive response to this aggressive action by the American enemy,” according to state TV.

Missile alert warnings sounded in Bahrain and Kuwait early Wednesday as they faced incoming Iranian fire — a daily occurrence in recent days. Jordan said it shot down three incoming Iranian missiles. Iran claimed attacks on the three nations, all of which host U.S. forces.

U.S. Navy Adm. Brad Cooper, who leads Central Command, said in a statement that Iran had launched dozens of missiles and drones at neighboring Gulf Arab countries.

Trump told the Fox News Channel on Tuesday night that more U.S. strikes against Iran would come over the next two days and that bridges and power plants could be targeted by next week unless negotiations resume. Already, the U.S. has struck at least one bridge.

“You better make a deal, or you’re not going to have anything left,” Trump warned.

Iran’s ambassador to the United Nations, Amir Saeid Iravani, criticized America’s attacks.

“The U.S. is the aggressor, not the victim,” he wrote to the world body’s leader, according to the state-run IRNA news agency.

The Strait of Hormuz remains at the heart of the fighting

The latest round of fighting is focused on the Strait of Hormuz, through which a fifth of the world’s oil and natural gas trade passes during peacetime. How to reopen the strait has bedeviled the U.S. since Iran choked it off in the early days of the war.

During the interim deal, some ships began moving through the passage using a route near Oman overseen by the U.S. military that is outside Tehran’s control.

In recent days, Iran attacked ships using that route — and back-and-forth attacks ensued. The U.S. has threatened to reopen the strait by force — but experts say that would require a much bigger armada if not tens of thousands of ground troops. Imposing the blockade is another way to put pressure on Iran.

But in the meantime, oil prices are rising. The price for Brent crude oil, the international standard, traded above $85 a barrel on Wednesday — more than 15% higher than the price before the war, but still well below the nearly $120 reached at the height of the conflict.

Analysts with the International Monetary Fund warned Wednesday that while a surplus of oil had kept prices low, “much of that room has now been used up.”

“As tensions flare again in the Strait of Hormuz, that room is now smaller and shrinking further as spare capacity has been deployed, demand has compressed, and inventories have been drawn down,” Azim Sadikov and Jean-Marc Natal wrote in a blog post. “Unless inventories are replenished, the world will start from a weaker position when the next shock comes.”

Regional mediators are still trying to get the United States and Iran back to the negotiating table.

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Associated Press writer Nasser Karimi in Tehran, Iran, contributed to this report.