President Donald Trump said Monday that the current US military operation in Iran is expected to last four to five weeks but could go on for longer if necessary.

"We projected four to five weeks, but we have capability to go far longer than that. We'll do it," Trump told a White House ceremony about the US’ Operation Epic Fury, which began on Saturday.

Trump said the operation is moving "ahead of schedule" but did not give further details.

The president framed the offensive’s duration as tied to the dismantling of Iran’s conventional missile infrastructure, calling it an urgent and expanding threat.

Trump said Iran's conventional ballistic missile program was growing "rapidly and dramatically."

"This posed a very clear, colossal threat to America and our forces stationed overseas, the regime already had missiles capable of hitting Europe and our bases, both local and overseas, and would soon have had missiles capable of reaching our beautiful America," he added.

Trump also said: “Today, the United States military continues to carry out large-scale combat operations in Iran to eliminate the grave threats posed to America by this terrible terrorist regime."

'We continue this mission with ferocious, unyielding resolve'

The current offensive is the US’ "last best chance" to strike and eliminate the "intolerable threats posed by this sick and sinister regime," he said of Iran.

"Our objectives are clear. First, we're destroying Iran's missile capabilities ... Second, we're annihilating their navy. We've knocked out already 10 ships. They're at the bottom of the sea.

"Third, we're ensuring that the world's number one sponsor of terror can never obtain a nuclear weapon. Never going to have a nuclear weapon. I said that from the beginning, never going to have a nuclear weapon.”

The US and Israel launched strikes against Iran on Feb. 28, killing the country's Supreme Leader Ali Khamenei and other top security officials.

Earlier, the US Central Command (CENTCOM) announced that four American service members were killed in action on day three of the US-Israeli joint attacks.

Commiserating with the service members' families, Trump pledged to continue with the operation.

"In their memory, we continue this mission with ferocious, unyielding resolve to crush the threat this terrorist regime poses to the American people," he said. (AA)

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