WASHINGTON • Defense Secretary Pete Hegseth spoke Monday to worries that the U.S.-Israeli strikes in Iran could spiral into a protracted regional conflict by declaring that the war won’t be endless.

“This is not Iraq. This is not endless,” said Hegseth, even as he warned that more American casualties are likely in the weeks ahead.

While the Trump administration has cited Iran’s nuclear ambitions as the chief concern to be addressed, officials increasingly are pointing to the threat from Iran’s ballistic missiles as a key reason to launch the attacks, as well as an opportunity to take out the government’s leadership and the sense that negotiations around the nuclear program have stalled.

Trump said Monday that Iran’s conventional missile program “was growing rapidly and dramatically, and this posed a very clear, colossal threat to America and our forces stationed overseas.”

Hegseth said at a separate press conference with Gen. Dan Caine, chairman of the Joint Chiefs of Staff, that the operation had a “decisive mission” to eliminate the threat of Iranian ballistic missiles, destroy the country’s navy and ensure “no nukes.”

The killing of Iranian Supreme Leader Ayatollah Ali Khamenei has cast doubt on the future of the Islamic Republic.

Caine said the biggest U.S. military buildup in the Middle East in decades would only grow because the commander in the region “will receive additional forces even today.”

Asked if there are boots on the ground now in Iran, Hegseth said, “No, but we’re not going to go into the exercise of what we will or will not do.”

He said it was “foolishness” to expect U.S. officials to say publicly “here’s exactly how far we’ll go.”

Hegseth also dismissed questions about the timeframe and said Trump had “latitude” to decide how long it would take.

“Four weeks, two weeks, six weeks,” he said. “It could move up. It could move back.”

In laying out a case for the strikes, Hegseth pointed to threats from other weaponry that justified the operation: “Iran was building powerful missiles and drones to create a conventional shield for their nuclear blackmail ambitions.”

He added, “Our bases, our people, our allies, all in their crosshairs. Iran had a conventional gun to our head as they tried to lie their way to a nuclear bomb.”

The Cabinet official said again that strikes by the U.S. and Israel last June “obliterated their nuclear program to rubble.”

Hegseth said that during negotiations leading up to the attack, Iranian officials were “stalling,” despite having “every chance to make a peaceful and sensible deal.”

He also justified the operation by describing Iran’s government as having started the conflict from its inception, declaring that, for 47 years, it has “waged a savage, one-sided war against America.”

On Monday, the White House said Iran has “killed and maimed American citizens and service members through its own forces and proxy militias,” adding that more Americans have been killed by the Islamic Republic “than any other terrorist regime on Earth.”

They included the April 1983 attack by the Iran-backed Islamic Jihad, which sent a suicide car bomb at the American embassy in Beirut. The attacked killed 17 Americans. The White House also noted the October 1983 attack by Hezbollah, also an Iran proxy, which killed 241 American military personnel in a truck bombing at a Marine compound also in Beirut.