The United States launched air strikes against Iranian forces and allied militias in Iraq and Syria on Friday, with President Joe Biden vowing more to come in retaliation for a deadly drone attack on an American base in Jordan.
The United States blamed Sunday's drone attack on forces backed by Iran, but did not strike inside the country's territory on Friday, with both Washington and Tehran seemingly keen to avoid all-out war.
"Our response began today. It will continue at times and places of our choosing," Biden said in a statement.
"The United States does not seek conflict in the Middle East or anywhere else in the world. But let all those who might seek to do us harm know this: If you harm an American, we will respond," he added.
The strikes targeted the Islamic Revolutionary Guard Corps (IRGC) Quds Force and "affiliated militia groups," with American forces -- including long-range bombers flown from the United States -- hitting "more than 85 targets," the US Central Command said in a statement.
"The airstrikes employed more than 125 precision munitions," it added. Targets included command and control and intelligence centers, as well as rocket, missile and drone storage facilities belonging to "militia groups and their IRGC sponsors who facilitated attacks against US and coalition forces."
The strikes killed at least 18 pro-Iran fighters in Syria's east, according to war monitor the Syrian Observatory for Human Rights.
General Yehia Rasool, a spokesman for Iraq's prime minister, called the strikes a "violation" of his country's sovereignty and said they would bring "disastrous consequences for the security and stability of Iraq and the region."
Prime Minister Mohamed Shia al-Sudani has recently called for the departure of international troops from Iraq after a previous US strike in Baghdad.
US National Security Council spokesman John Kirby said Washington "did inform the Iraqi government prior to the strikes," but did not elaborate on Baghdad's response.
Kirby told journalists the strikes lasted about 30 minutes, though they involved a lengthy trip for the B-1 bombers that flew from the United States.
He said the Defense Department was still assessing damage from the strikes, but added the United States believed they were successful and made clear that more would follow.
Syrian Observatory for Human Rights chief Rami Abdel Rahman said that at least 26 major sites housing pro-Iranian groups were destroyed in Syria, including weapons depots.
A weapons warehouse and a command center belonging to pro-Iranian groups were also targeted in western Iraq, along the Syrian border, two Iraq security sources told AFP, resulting in at least "some injuries."
The strikes represent a "significant escalation," according to Allison McManus, managing director for national security and international policy at the Center for American Progress.
But she was skeptical about the impact, adding: "We have not seen that similar tit-for-tat strikes have had a deterrent effect."
- 'Dignified transfer' -
Biden earlier Friday attended a solemn military ritual at a Delaware air base for the return of the three soldiers killed in the drone attack in Jordan.
Pentagon chief Lloyd Austin and the chairman of the Joint Chiefs of Staff, General Charles "CQ" Brown, also attended what is known as the "dignified transfer" -- their presence highlighting the relative rarity of returning dead US service members in the wake of the exit from Afghanistan in 2021.
The soldiers killed Sunday were the first American military deaths from hostile fire in the Middle East since the start of a spike in attacks on US and allied forces in the wake of Hamas's surprise October 7 assault on Israel.
That attack sparked a devastating Israeli campaign in Gaza, which has stoked tensions and violence across the Middle East and dragged it ever closer to a full-on regional conflict.
US and coalition troops have been attacked more than 165 times in Iraq, Syria and Jordan since mid-October with weapons including drones, rockets and short-range ballistic missiles.
Dozens of American personnel have been wounded in previous attacks, many of which have been claimed by a loose alliance of Iran-linked armed groups that oppose US support for Israel in the Gaza conflict and want American troops out of the region.
With Biden running for reelection this year, Republican Speaker of the House Mike Johnson criticized his operation as too little, too late.
"Unfortunately, the administration waited for a week and telegraphed to the world, including to Iran, the nature of our response," he said in a statement Friday.
"The public handwringing and excessive signaling undercuts our ability to put a decisive end to the barrage of attacks endured over the past few months."
Yemen's Iran-backed Huthi rebels, meanwhile, began targeting international shipping in the Red Sea in November, sparking US and British air strikes aimed at curbing the aggression which in turn have led to attempted attacks on US naval vessels.