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The rubble of a destroyed building, seen from inside a heavily damaged building, after an Israeli strike in Tyre, Lebanon on Thursday.Yara Nardi/Reuters

Dozens of countries sought ways to restart vital energy shipments through the Strait of Hormuz on Thursday after U.S. President Donald Trump vowed more aggressive strikes on Iran, sending oil prices higher again and deepening strain on consumers.

In a speech on Wednesday night, Trump said operations would be intensified and gave no timeline for ending hostilities, drawing threats of retaliation from Tehran and depressing share prices.

“We’re going to hit them extremely hard over the next two to three weeks. We’re going to bring them back to the Stone Ages where they belong,” Trump said in the speech amid mounting domestic pressure to end the conflict.

Britain chaired a virtual meeting on Thursday of some 40 countries to explore ways to restore freedom of navigation that did not produce any specific agreement, although participants agreed that all nations should be able to use the waterway freely, one official said.

Trump persisted with his threats on Thursday, saying in a social media post: “IT IS TIME FOR IRAN TO MAKE A DEAL BEFORE IT IS TOO LATE.” He also posted footage of what appeared to be strikes on a bridge in Iran.

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Iran has effectively shut down the Strait of Hormuz, which normally carries about a fifth of the world’s total oil consumption, in retaliation for U.S.-Israeli strikes that began on February 28. The war has caused a spike in oil prices, inflation concerns, supply-chain problems and worries about the impact on the global economy.

Still defiant despite the death of a slew of its leaders, Tehran offered a competing vision for future control of the strait, and said it was drafting a protocol with Oman that would require ships to obtain permits and licenses.

“These requirements will not mean restrictions, but rather to facilitate and ensure safe passage and provide better services to ships that pass through this route,” Deputy Foreign Minister Kazem Gharibabadi said, according to the official IRNA news agency.

An Iranian military spokesperson on Thursday said the strait would remain closed “long term” to the U.S. and Israel.

The European Union’s foreign policy chief Kaja Kallas pushed back against Tehran’s plan, saying Iran cannot be allowed to charge countries a bounty to let ships pass. “International law doesn’t recognize pay-to-pass schemes,” wrote Kallas on X.

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Benchmark Brent crude prices jumped by about 7 per cent to around US$108 per barrel, U.S. bond yields spiked and global equity markets gave back gains.

“The key question in all investors’ minds is ’When is this going to be over?’” said Russel Chesler, head of investments and capital markets at VanEck Australia.

Trump warned that the war could escalate if Iran did not give in to Washington’s terms, with strikes on its energy and oil infrastructure possible. He told countries that rely on fuel shipments through the Strait of Hormuz to “just grab it.”

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A cargo ship in the Gulf, near the Strait of Hormuz, as seen from northern Ras al-Khaimah, near the border with Oman’s Musandam governance on March 11.Stringer/Reuters

However, European and other states have said they will only help secure the strait if there is a ceasefire.

“It can only be done in consultation with Iran,” French President Emmanuel Macron said.

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Iran’s armed forces responded to Trump with a warning of “more crushing, broader and more destructive” attacks in store.

The war will continue until the “permanent regret and surrender” of Iran’s enemies, said Ebrahim Zolfaqari, spokesperson for the Iranian military’s Khatam al-Anbiya central headquarters, in a statement carried by Iranian media.

Iran’s Fars news agency later listed several bridges in Saudi Arabia, Kuwait, Abu Dhabi and Jordan as potential targets for Iranian military operations after one of its own bridges was hit by air strikes. The Revolutionary Guards said they had targeted an Amazon cloud computing centre in Bahrain.

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Men ride a scooter past the rubble of a building destroyed by an Israeli strike in Tyre, Lebanon.Yara Nardi/Reuters

There are fears the conflict may leave Iran with a stranglehold over Middle East energy supplies now that it has shown that it can block the Strait of Hormuz by targeting oil tankers and attacking Gulf countries hosting U.S. troops.

Gulf states say they reserve the right to self-defence but have refrained from responding militarily to repeated Iranian attacks over the past month, seeking to avoid escalation into a far more devastating all-out Middle East war.

Iran’s parliament was reviewing a bill that would formalize the blocking of vessels from hostile countries passing through the strait and the charging of tolls for others wishing to pass, spokesperson Abbas Goodarzi said.

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Thousands of people have been killed and tens of thousands injured across the Middle East since the war began, with the head of the International Federation of Red Cross and Red Crescent Societies delegation saying on Thursday that medical needs were rising exponentially and supplies could run low.

Iran’s state media said eight people were killed and 95 wounded when a bridge linking Tehran and the western city of Karaj was hit by air strikes. Some large steel producers and Tehran’s Pasteur Institute of Iran medical research centre were separately reported to have sustained serious damage.

The Revolutionary Guards said they had targeted U.S.-linked steel and aluminum facilities in Gulf states and an Oracle data centre in Dubai, and would step up such attacks if Iranian industries were hit again.

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Israeli security forces and first responders work at the site of an impact in a residential neighbourhood of Tel Aviv following an Iranian strike on Wednesday.JACK GUEZ/AFP/Getty Images

Sirens and the booms from interceptors rang out over Jerusalem after the Israeli military said it had identified the launch of a missile from Yemen toward Israel.

Yemen’s Iran-aligned Houthis first claimed an attack on Israel at the end of March, as the conflict with Iran has expanded across the region.

Fuel shortages have already caused economic strains across Asia and are expected to bite in Europe soon, while a report by two UN agencies warned a sharp economic slowdown could spark a cost-of-living crisis in Africa.