Sgt. Benjamin N. Pennington, 26, was killed in Saudi Arabia.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israel strikes attack targeting military and government sites, officials said.
Iranian state television confirmed that Ayatollah Ali Khamenei was among those killed in Tehran on the first day of strikes. His son Mojtaba Khamenei was chosen on Sunday to succeed him.
Iran is responding to the operation with missile and drone attacks targeting Israel, regional U.S. bases and multiple Gulf nations. Israel is also intensifying its long-running strike campaign against the Iran-backed Hezbollah militia in Lebanon.
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White House press secretary Karoline Leavitt said U.S. ground troops in Iran are "not part of the plan" at present.
"They're not part of the plan for this operation at this time, but I certainly will never take away military options on behalf of the president of the United States or the commander in chief, and he wisely does not do the same for himself," Leavitt said at a press briefing Wednesday afternoon.
President Donald Trump will attend the dignified transfer of the six U.S. service members killed in this weekend's retaliatory attack by Iran, White House press secretary Karoline Leavitt said Wednesday.
Four of the six have been identified: Capt. Cody A. Khork, 35, of Winter Haven, Florida; Sgt. 1st Class Noah L. Tietjens, 42, of Bellevue, Nebraska; Sgt. 1st Class Nicole M. Amor, 39, of White Bear Lake, Minnesota; and Sgt. Declan J. Coady, 20, of West Des Moines, Iowa. All four died Saturday in Kuwait from an Iranian drone attack.
MORE | Iowa soldier killed in Kuwait remembered by family as 'smart and kind'
Iran's top national security official on Wednesday warned the U.S. and Israel that the killing of Iranian Supreme Leader Ali Khamenei "will exact a heavy price from you."
"Mr. Trump, with Netanyahu's clownish antics, dragged the American people into an unfair war with Iran," Ali Larijani, secretary of Iran's Supreme National Security Council, wrote in a post on X. "Now let him do the math: with over 500 American troops killed (in these past few days), is it still 'America First,' or 'Israel First'? The saga continues."
"The martyrdom of Imam Khamenei will exact a heavy price from you. God willing," he added.
CENTCOM has confirmed that six Americans have been killed in the attacks.
-ABC News' Somayeh Malekian
"The evidence in front of us since the 12-day war was that Iran had no intention of actually negotiating a nuclear deal that truly meant they did not have a pathway to the nuclear bomb," Defense Secretary Hegseth said at the Pentagon briefing.
Hegseth said that negotiators Jared Kushner and Steve Witkoff "poured into that negotiation, giving them every single possible opportunity to release that that ambition, and they didn't. And the intelligence that we saw (showed) they didn't intend to do it in good faith - that they had the intentions eventually to get to a place where they could have that a conventional shield to block their nuclear capabilities."
-ABC News Steve Beynon
