WASHINGTON — The USA carried out airstrikes early Monday morning in Iraq and Syria towards two Iranian-backed militias that the Pentagon stated had carried out drone strikes towards American personnel in Iraq in latest weeks, the Protection Division stated.

“At President Biden’s path, U.S. navy forces earlier this night conducted defensive precision airstrikes towards amenities utilized by Iran-backed militia teams within the Iraq-Syria border area,” the Pentagon spokesman, John F. Kirby, stated in a press release.

Mr. Kirby stated the amenities have been utilized by Iranian-backed militias, together with Kata’ib Hezbollah and Kata’ib Sayyid al-Shuhada, to retailer arms and ammunition for finishing up assaults towards locations the place Individuals have been positioned in Iraq. There have been no rapid reviews of casualties however a navy after-action assessment is ongoing, Pentagon officers stated.

The strikes have been the second time that Mr. Biden has ordered using drive within the area. The USA carried out airstrikes in eastern Syria in late February towards buildings belonging to what the Pentagon stated have been Iran-backed militias chargeable for assaults towards American and allied personnel in Iraq.

The newest strikes have been carried out by U.S. Air Drive fighter-bombers based mostly within the area.

Pentagon planners have been gathering info for weeks on the websites and militia networks that use them, American officers stated on Sunday. Protection Secretary Lloyd J. Austin III and Gen. Mark A. Milley, the chairman of the Joint Chiefs of Employees, briefed Mr. Biden on assault choices early final week, and Mr. Biden accredited placing the three targets, the officers stated.

The strikes have been carried out a bit greater than every week after Iran elected a hard-liner, Ebrahim Raisi, as its subsequent president.

The navy motion additionally got here because the negotiations meant to carry america and Tehran again into compliance with a world nuclear accord have reached an important juncture. President Donald J. Trump pulled the United States out of the accord in 2018, and Mr. Biden has been searching for to revive it.

On Sunday, Secretary of State Antony J. Blinken mentioned the negotiations on the nuclear cope with Israel’s overseas minister, Yair Lapid, who stated Israel had “critical reservations” in regards to the accord, which might ease sanctions on Iran in return for limits on its nuclear program.

Earlier this month, the Biden administration blocked entry to myriad web sites linked to Iran after the nation held a presidential vote to put in Mr. Raisi, a detailed ally of the clerical authorities’s supreme chief, as its high elected official.

Stress has been constructing for weeks from Democrats and Republicans in Congress, and from a few of Mr. Biden’s high advisers and commanders, to retaliate towards the risk posed by the drones to American diplomats and the two,500 U.S. troops in Iraq who’re coaching and advising Iraqi forces.

No less than 5 occasions since April, the Iranian-backed militias have used small, explosive-laden drones that divebomb and crash into their targets in late-night assaults on Iraqi bases — together with these utilized by the C.I.A. and U.S. Particular Operations models, in line with American officers. To date, no Individuals have been harm within the assaults, however officers fear in regards to the precision of the drones, additionally known as unmanned aerial automobiles, or U.A.V.s.

The drones are a part of a quickly evolving risk from Iranian proxies in Iraq, with militia forces specialised in working extra subtle weaponry hitting a few of the most delicate American targets in assaults that evaded U.S. defenses.

Iran — weakened by years of harsh financial sanctions — is utilizing its proxy militias in Iraq to step up stress on america and different world powers to barter an easing of these sanctions as a part of a potential revival of the 2015 nuclear deal. Iraqi and American officers say Iran has devised the drone assaults to reduce casualties to keep away from prompting U.S. retaliation.

American officers stated the strikes — towards two targets in jap Syria and a 3rd simply throughout the border in Iraq — have been carried out about 1 a.m. Monday native time by a mixture of Air Drive F-16s and F-15Es based mostly within the area.

The fighter-bombers dropped a number of bombs — 500-pound and a pair of,000-pound satellite-guided munitions — on every of the three constructions. American officers stated the militias used the websites focused in Syria primarily for storage and logistics functions; the location hit in Iraq was used to launch and get well the armed drones, which officers stated have been both made in Iran or used Iranian know-how.

Mr. Kirby and different administration officers characterised the strikes as defensive, however main lawmakers demanded extra particulars on Sunday.

“Congress should be briefed on these airstrikes at once,” stated Senator Tim Kaine, Democrat of Virginia, who has led the struggle to restrict presidential conflict powers for a decade from the Senate International Relations Committee. “If the strikes have been towards militias that have been utilizing U.A.V.s to assault American personnel, that will be a standard self-defense motion that’s justified. However we have to know extra.”

Michael P. Mulroy, a former C.I.A. officer and high Center East coverage official on the Pentagon, has warned that with the know-how supplied by Iran’s Quds Drive — the foreign-facing arm of Iran’s safety equipment — the drones are quickly turning into extra subtle at a comparatively low value.

“This motion ought to ship a message to Iran that it can’t conceal behind its proxy forces to assault america and our Iraqi companions,” Mr. Mulroy stated on Sunday.

However Mr. Biden’s high aides have additionally stated they need to keep away from the offended rhetorical jabs and tit-for-tat threats that Mr. Trump usually engaged in with Iran and its proxies in Iraq, and keep away from escalating tensions with Tehran at a time when the White Home is attempting to nail down the nuclear deal.

The airstrikes in February towards the identical militias have been additionally a comparatively small, fastidiously calibrated navy response: seven 500-pound bombs dropped on a small cluster of buildings at an unofficial crossing on the Syria-Iraq border used to smuggle throughout weapons and fighters.

These earlier strikes have been simply over the border in Syria to keep away from diplomatic blowback to the Iraqi authorities. The identical calculus influenced the planning for the strike on Monday — two of the three targets have been in Syria alongside the Iraqi border, and the third was simply inside Iraqi territory. The strikes befell early Monday partly to keep away from any civilian casualties, officers stated.

“The USA took obligatory, acceptable and deliberate motion designed to restrict the chance of escalation — but additionally to ship a transparent and unambiguous deterrent message,” Mr. Kirby stated.

How the militias and Iran will reply is unclear, and American officers stated the comparatively small set of airstrikes have been unlikely to cease the militia assaults fully. After the February strikes, there was a lull in militia exercise towards American areas for a number of weeks, however then an much more harmful risk emerged: the small armed drones.

Jennifer Steinhauer, Julian Barnes and John Ismay contributed reporting.