The U.S. military has reinstated a naval blockade and bombed Iran for several consecutive days, concentrating attacks on coastal areas near the Strait of Hormuz. But airstrikes have recently extended to infrastructure, such as railways that could be used to ferry weapons.

On Saturday, the U.S. military announced a new wave of airstrikes in retaliation for the deaths.

“The strikes are designed to further degrade Iran’s ability to threaten commercial shipping in the Strait of Hormuz and swiftly punish Islamic Revolutionary Guard Corps forces who launched attacks against American service members in Jordan last night,” U.S. Central Command said.

At the same time, Iran has launched attacks on commercial ships and at its neighbors across the Persian Gulf region, targeting U.S. military assets. Tehran has also hit energy infrastructure and even water desalination plants.

Still, fighting hasn’t been as extensive as it was during the initial phases of the war. But U.S. deaths previously represented a red line for President Donald Trump.

Early last month—before both sides signed a memorandum of understanding that has since collapsed—he confided to aides that he would consider ending the prior ceasefire and go back to war if Iran kills American troops, according to the Wall Street Journal.

When asked for a comment and whether the U.S. would return to all-out war, the White House only responded with a statement from Central Command announcing the casualties.

Oil prices have jumped as fighting has intensified in recent days, and more war would deliver another shock to global markets.

Consuming countries have drawn down their oil stockpiles to the lowest level in decades with little breathing room left to endure another extended closure of the Strait of Hormuz.

The U.S. established an alternate route through the narrow water to bypass an Iranian corridor, but the renewed fighting has effectively it shut down.

On Friday, no crossings via the U.S.-backed route were detected, and no shadow fleet movements were recorded either, while Iran’s route saw seven transits.

Despite the massive U.S.-Israeli bombardment, the war didn’t bring about an overthrow of Iran’s regime and has failed to fully reopen the strait.

To be sure, Iran’s economy is reeling and conventional forces were decimated, but the Islamic Republic has enough combat power to scare away commercial shipping and isn’t deterred from continuing its attacks.

Meanwhile, hopes for a new round of talks to cobble together another ceasefire are vanishing. Previously, some officials appeared to leave the door open to negotiations despite Tehran’s defiant statements in the face of U.S. strikes.

That’s after pragmatists inside Iran privately admitted that the initial naval blockade had crushed the economy, with the blockade’s resumption reportedly deepening a rift between pragmatists and hard-liners who want to fight more aggressively.

But on Saturday, Iran’s supreme leader warned of “unforgettable lessons” if the U.S. keeps attacking and called Trump’s signature “worthless and invalid.” 

For its part, the U.S. blames Iran for violating the ceasefire agreement by refusing to reopen the strait and attacking ships sailing outside of Tehran’s approved corridor.

The stalemate has raised fears of an endless war, something Trump campaigned on avoiding, as tit-for-tat attacks continue along an escalating spiral.

“The immediate dispute concerns who controls the Strait of Hormuz, but more is at stake,” Ali Vaez, the Iran Project Director at the International Crisis Group, wrote in a New York Times op-ed on Wednesday. “The collapse of even this minimal understanding could remove the last barrier between episodic confrontation and a forever war.”

Gregory Brew, senior analyst for Iran and energy with the Eurasia Group, told Fortune’s Jordan Blum earlier that there’s no military option for reopening the strait, adding that Iran will not let go of its main source of leverage.

He also warned that some form of Iranian fee to cross the strait seems inevitable and that U.S. attacks only strengthen Tehran’s resolve.

“The options are to escalate or cut a deal. And I think the [Trump] administration is likely to do the first, see it fail, and end up with the second,” Brew predicted.