BEIRUT — It has been one setback after another for Iran — the loss of its own and allied military commanders in Israeli strikes, death and disarray in the ranks of Hezbollah and, in response, a ballistic missile attack on Israel whose destruction appeared limited.

Former U.S. officials and analysts worry that Iran’s conventional losses are exactly the kind of development that could trigger a final dash to the bomb. Iran has spent years moving ever closer to acquiring a capability for nuclear weapons since then-President Donald Trump scuttled the Iran nuclear deal in 2018, according to U.S. and U.N. assessments.

Now, even short of a move toward weaponization, Iran may be willing to increase use of its potential nuclear status to deter its adversaries. And that appears to be informing Israeli leaders as they consider a response to the barrage of around 180 ballistic missiles.

“Iran made a big mistake tonight, and it will pay for it,” Israeli Prime Minister Benjamin Netanyahu warned after Tuesday’s attack. “The regime in Iran does not understand our determination to defend ourselves and to retaliate against our enemies.”

While visually spectacular — videos of Iranian missiles lighting up the Tel Aviv sky played on a loop on Iranian state television for days — the munitions that actually made it though Israel’s defenses don’t appear to have caused the extensive damage Iran intended.

The attack was “extraordinary,” “legal” and “legitimate,” said Iran’s supreme leader, Ayatollah Ali Khamenei, while leading Friday prayers in Tehran. But his remarks also struck a somber tone, acknowledging recent losses, particularly the assassination of Hezbollah leader Hasan Nasrallah, whom he praised as a “brother” and “shining jewel of Lebanon.”

Khamenei vowed that Iran’s support for the resistance was unwavering and called on the country’s allies to “tighten the belt of defense.” Moving forward, he said Iran will “neither procrastinate nor hurry in doing our duty.

Iran’s defensive posture, however, has taken a number of hits over the past year as Israel has waged war on Hamas in Gaza, launched airstrikes against the Houthis in Yemen, and most recently narrowed its focus on Hezbollah in Lebanon. All three groups, along with militias in Iraq and Syria, make up Iran’s “axis of resistance,” a loose network of allied groups that were established in part to insulate Tehran from regional threats.

“If the axis of resistance isn’t working then the only deterrent might be a nuclear deterrent,” said David Albright, a nuclear weapons expert and president of the Institute for Science and International Security, a Washington nonprofit. The weakening of Hamas and Hezbollah, combined with Iran’s failure to inflict significant damage on Israel with its missile strikes, means “there’s a better chance Iran could decide to build nuclear weapons,” he said.

Losses to Hezbollah have been particularly devastating for Iran.

“When you think of a chess board, Hezbollah is Iran’s queen. It’s the most successful militia force that Iran created,” said Sina Azodi, an expert on Iran and a lecturer at George Washington University. The degradation of Hezbollah leaves Iran more exposed, because it “gives Israel more freedom of action in the region,” Azodi said.

Inside Iran, there was an abrupt shift in rhetoric around nuclear weapons in the weeks after the Oct. 7 Hamas attack on Israel and Israel’s subsequent invasion of Gaza. Previously, Iranian leaders had denied having any intention to develop nuclear weapons. But over the past year, in speeches and interviews, officials have asserted that Tehran already possessed everything it needed for a nuclear weapon but had opted to exercise restraint.

“In terms of our national security, we do not want to do it,” Mohammad Eslami, head of the Atomic Energy Organization of Iran, said in January. “It is not about the lack of capability.”

A report issued by the U.S. Office of the Director of National Intelligence in February described the Iranian nuclear threat in starker terms compared with previous assessments. While Iran does not appear to be actively developing a weapon, Tehran since 2020 “has stated that it is no longer constrained by” the nuclear deal’s limits and has “undertaken activities that better position it to produce a nuclear device, if it chooses to do so,” the report said.

Under the 2015 Iran nuclear accord, negotiated by the United States and five other world powers plus the European Union, Iran agreed to accept severe curbs on its nuclear program, including tight limits on the amount of enriched uranium it could possess, as well as intrusive monitoring by the International Atomic Energy Agency, the Vienna-based nuclear watchdog.

But after Trump’s withdrawal from the deal, Iran threw off most of its restraints and began producing enriched uranium at an ever faster rate, according to U.S. and IAEA assessments.

Most worryingly, Iran last year began stockpiling a form of highly enriched uranium that is close to weapons grade, according to confidential IAEA reports. U.S. officials confirm that Iran could use this fuel to create a bomb’s worth of weapons-grade uranium in as little as a few days, if it chooses to do so.

Iran would need additional time — a few months or even a year or more — to master the technology to build a reliable nuclear warhead that could be delivered by one of its ballistic missiles, officials and experts said.

The next step that U.S. officials and regional diplomats are watching will be Israel’s response to Iran’s missile attack. Iranian officials have already warned that an Israeli response will be met with attacks on energy infrastructure, without specifying where. Iranian allies in Iraq have made similar threats.

“If the energy war begins, the world will lose 12 million barrels of oil per day. Either everyone will enjoy the blessings of energy, or everyone will be deprived,” said Abu Ali al-Askari, of the powerful Iranian-allied militia Kataib Hezbollah in Iraq.

Several current and former U.S. officials expressed concerns that Israel may seize on an opportunity to attack Iran’s uranium enrichment facilities as retaliation for this week’s missile strike. But whether Israeli bombs could penetrate Iran’s most deeply buried uranium plants is unclear, the officials and weapons experts said. Much of Iran’s highly enriched uranium, they said, is made at its Fordow enrichment plant, which was built inside tunnels dug into a mountain near the city of Qom.

“It is highly likely that this time Israelis will target Iranian nuclear facilities, especially if they believe Iran has already resumed nuclear weaponization work,” said Gregory Koblentz, an associate professor and nonproliferation expert at George Mason University’s Schar School of Policy and Government. Koblentz said Israel’s attacks against Hezbollah in recent weeks were partly intended to neutralize the group’s vast rocket and missile forces, which were “widely seen as Iran’s insurance policy against an Israeli attack on their nuclear facilities.”

“With Hezbollah functionally disarmed, for now, Israel has a window of opportunity to strike Iranian nuclear sites and a low risk of retaliation from Hezbollah,” Koblenz said.

Yet, even a successful Israeli strike might only delay Iran’s race to a bomb, officials said. One former White House adviser on nonproliferation said an attack on Iran’s main enrichment facilities would “set back, not end the program.”

Such a move could even harden Iran’s resolve, said the former official, who spoke on the condition of anonymity to conform with his current employer’s policies.

“It could lead to a change in Iranian nuclear intentions — going from a covert threshold program to an overt weapons program,” the former official said.

“It could — and likely would — lead to an Iranian escalation.”

Warrick reported from Washington. Mustafa Salim in Baghdad contributed to this report.

previous coverage

• EU moves to sanction Iran for providing missiles to Russia
• Israel’s Arrow says missile defense systems did their job against Iran