The U.S. and Iran traded heavier strikes Thursday as a weeklong escalation threatened to unravel last month's truce, though Tehran's release of a U.S. citizen raised hopes of averting a return to full-scale war.

For the first time since a memorandum of understanding (MoU) paused ⁠fighting last month, the United States launched two big waves of airstrikes in ⁠one day Wednesday, mostly on targets near the coast in southern Iran.

Iran responded with missiles and drones fired at U.S. military bases in neighboring countries, including a major barrage at a recently expanded air base in Jordan.

The week of increasingly intense fire has tested the limits of escalation that both sides ​set during four months of fighting before last month's truce. But in the midst of the attacks, U.S. President Donald Trump ​hailed ⁠the release of a U.S. citizen in Iran as a "gesture of goodwill."

Human rights lawyer Jared Genser identified her as Dena Karari, who he said had been "trapped in Iran since December 2024 on bogus charges" and was "now safe and traveling back to the United States." There was no comment from Iran on the case.

Over decades of confrontation, the release of U.S. citizens held in Iran has been managed through behind-the-scenes contacts that persisted when formal diplomacy was cut off.

The re-escalation has once again nearly halted traffic through the Strait of Hormuz, the world's most important shipping route for oil and gas, sending global energy prices shooting higher. But prices are still well below wartime peaks, suggesting traders anticipate the crisis could abate.

Iran triggered the renewed fighting last week by striking ships using a corridor in the strait outside its control, including a drone attack that caused a dangerous fire on board a Qatari tanker filled with liquefied natural gas.

Tehran officials said Thursday that the Strait was an inviolable "red line," warning that if Trump carried out his threat to attack Iran's infrastructure, it ⁠would strike all infrastructure across the Gulf region.

Hormuz 'red line'

Iranian army spokesperson Brigadier General Mohammad Akraminia said Thursday that Hormuz, which carried about a fifth of global oil and gas shipments before the war, was a "red line" for Iran over which it maintains firm control.

"The Americans thought that by attacking some of our bases on the southern coasts of the country, they could take control of this strategic strait," Akraminia said.

"However, the Islamic Republic of Iran has the ability to exert control over the Strait of Hormuz from every single point of its territory, and this matter is never dependent on coasts and islands."

Three U.S. officials told Reuters that U.S. strikes aimed at forcing open the strait are also targeting Iranian military capabilities the U.S. would want to destroy before executing more complex operations.

Iran's army earlier said in reference ⁠to ⁠the strait: "We will undoubtedly resist until the end and will neutralize American interventions in the region."

Iran's military spokesperson has said that the only way to reopen the Strait of Hormuz was for the U.S. to comply with the 14-point memorandum of understanding that the two sides signed in June, and the implementation of "Iranian regulations" regarding ship traffic in the strait.

Iranian sources have told Reuters that Iran's aim was to establish its authority over the strait. But having made that point, Tehran is not keen for a wider escalation that would torpedo the June memorandum of understanding, which it still regards as giving it most of what it sought.

Trump has declared the ⁠cease-fire ⁠under the memorandum "over."

Within Iran, the renewed bombing has left residents anxious, following huge weeklong memorial events for slain Supreme Leader Ayatollah Ali Khamenei that the authorities depicted as a demonstration of victory and national solidarity.

"Living with this fear that war could start again is very exhausting. You cannot live like this. We are tired of war. What is our sin that we have to live this way? Personally, I want diplomacy to prevail," Mahlegha, 46, a government employee, told Reuters by phone message from Tehran.

Iran wants all ships using the Strait of Hormuz to travel only through a channel close to its shores and has made no secret that it intends to charge passage fees at the end of a 60-day negotiation period set in last month's memorandum.