Another American soldier has died after a "controlled explosion" of an Iranian drone.
The US military confirmed on Sunday night that a serviceman had been killed, with US Central Command describing it as "a controlled detonation of unexploded ordnance from a downed Iranian one-way attack drone".
A second soldier was hurt in the same blast.
The death raises the confirmed American death toll this weekend alone to three.
A fourth service member is missing and presumed dead following an Iranian missile attack on a US base in Jordan.
Two soldiers were killed on Friday when Iranian missiles and drones struck Muwaffaq Salti Air Base in eastern Jordan, with several others wounded in that assault.
The military has not released the names of the dead.
Donald Trump described the deaths as "a shame" but maintained the military mission was vital.
"They did it because they don't want to see Iran have a nuclear weapon," Mr Trump said of the troops. "And it just shows you how bad [the Iranians] are."
Donald Trump described the deaths as 'a shame'
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Defence Secretary Pete Hegseth said "the deaths of the fallen only strengthen our resolve".
The weekend's casualties bring the total American military deaths in the conflict to 17, with at least 430 more injured.
US forces carried out their eighth straight night of airstrikes on Sunday, targeting Iranian coastal surveillance systems, air defence installations, maritime assets, and weapons storage facilities.
Centcom said the strikes were "designed to further degrade Iran's ability to threaten commercial shipping in the Strait of Hormuz and swiftly punish Islamic Revolutionary Guard Corps forces who launched attacks against American service members in Jordan".
Tehran's Atomic Energy Organisation accused American forces of attacking the Darkhovin nuclear power plant in southwestern Iran.
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PICTURED: US troops gear up for an eighth night of strikes in a row against Iran
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The UN's International Atomic Energy Agency said it was examining the claims - and that the facility is still only being built, and held no nuclear material during its last inspection.
The IAEA confirmed the incident posed no radiological danger.
Rafael Grossi, the body's director, reiterated his "call for military restraint in the vicinity of all nuclear-related sites".
Iran struck back on Sunday morning with attacks on Gulf allies.
Kuwait reported missile and drone strikes hitting a power station and water desalination plant.
PICTURED: A heavily-damaged bridge which was hit by a US strike is pictured along the road connecting Roudan and Bandar Abbas in southern Iran
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Air raid sirens rang out across Bahrain, with authorities urging locals to seek shelter.
Iran's state news agency IRNA claimed the Kuwait strikes targeted American ammunition stores at Camp Buehring and Patriot missile systems at Ali al Salem Air Base.
IRNA described the attacks as retaliation for "the enemy's repeated aggressions".
Jordan summoned Iran's charge d'affaires in Amman, condemning what it called "unjustified and blatant Iranian attacks" and "provocative and inflammatory statements targeting the Kingdom's territory".
Israeli and Jordanian forces intercepted an Iranian missile heading towards the Jordanian city of Aqaba.
Israel Katz, the Israeli Defence Minister, warned: "If Iran fires missiles at Israel, we will attack them with full force."