US Defence Secretary Pete Hegseth said the United States was winning its military operation against Iran "decisively, devastatingly and without mercy" and pledged to commit more forces to the campaign, speaking from the Pentagon on March 4.

"We will take all the time we need to make sure that we succeed," Hegseth said, adding that additional jet fighters and bombers would arrive in the region soon.

More than 1,000 people have been killed in less than seven days in the US-Israeli joint war on the Islamic Republic, with thousands more injured in the repeated attacks.

Hegseth confirmed that a US submarine sank an Iranian warship with a torpedo on the night of March 3, describing it as the first such attack on an enemy vessel since World War Two. "An American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo," he said.

The defence secretary said the US military had used more advanced weapons at the start of the campaign but was now switching to gravity bombs after establishing control of Iranian skies. He said stockpiles of advanced munitions remained "extremely strong."

Chairman of the Joint Chiefs of Staff General Dan Caine said C-17 military transport aircraft were being used to help American citizens flee the region. He declined to comment on the possibility of deploying ground troops in Iran, saying: "That's a question for policymakers. I don't make policy, I execute policy."

An Israeli military official told the AP that top US and Israeli commanders began planning the opening strike three weeks prior to the operation, and that senior Israeli officers went home for the weekend on February 27 to deceive Iran into thinking an attack was not imminent.

NATO condemned what it called Iran's "targeting of Turkey" after a ballistic missile was detected heading toward Turkish airspace on March 4 and intercepted. Turkish Foreign Minister Hakan Fidan spoke by phone with his Iranian counterpart Abbas Araghchi, with Ankara stressing that "all steps that could escalate the conflict" must be avoided.

A separate attack on a container ship transiting the Strait of Hormuz off the coast of Oman caused a fire in the vessel's engine room, the UK Maritime Trade Operations agency reported.

Ayatollah Ahmad Khatami, a member of the Assembly of Experts responsible for selecting a new supreme leader, said on Iranian state television that "the options have become clear," with other senior officials indicating a decision on Ayatollah Khamenei's successor could be close.