Enemy drone that hit US base in Jordan possibly confused with American drone, officials say

The working theory about how an enemy drone slipped past defenses at a U.S. base in Jordan is that American personnel mistook the enemy drone for one of their own returning from a surveillance mission, two U.S. officials confirmed Monday.

One U.S. official confirmed that the enemy attack drone approached the base at a low altitude and hit a housing area at the Tower 22.

The attack on Sunday by Iran-backed militants killed three American service members and wounded at least 34 others, U.S. officials said, with President Joe Biden warning that the strike will be met with American retaliation as Iran denied involvement.

The Pentagon on Monday announced the names of the three Army reservists killed as Sgt. William Jerome Rivers, 46, of Carrollton, Georgia.; Spc. Kennedy Ladon Sanders, 24, of Waycross, Georgia.; and Spc. Breonna Alexsondria Moffett, 23, of Savannah, Georgia., all from an Army Reserve engineering unit from Georgia.

At a Monday briefing, while Pentagon deputy press secretary Sabrina Singh couldn't say where the one-way attack drone came from, she said it had the "footprint of Kataib Hezbollah" and that U.S. officials believe Iran is behind the attack.

The drone hit early in the morning while many troops were still in bed, she added.

"Iran continues to arm and equip these groups to launch these attacks, and we will certainly hold them responsible," she said, adding, "We don't seek a wider conflict with Iran. We don't want to go to we don't want a war with Iran."

The deaths are expected to spur more U.S. involvement in the region since they mark the first in the line of fire for American troops since the start of the Israel-Hamas war in October in response to Hamas' terror attack.

RELATED: Pentagon identifies Army reservists killed in drone attack on US base in Jordan

The U.S. has supported Israel against Hamas in Gaza while trying to prevent the fighting from enveloping the broader Middle East, even as the U.S. has said Iran-supported militants carried out a series of strikes in Iraq, Syria and Yemen in opposition to Israel's campaign.

But Pentagon officials have also said that the deaths of American service members would elicit a strong response -- though such a step could draw the U.S. and other regional and international powers further into a mushrooming conflict.

"Have no doubt -- we will hold all those responsible to account at a time and in a manner our choosing," Biden said in a statement Sunday.

Later, during an event in South Carolina, Biden held a moment of silence for the dead and said, "We shall respond."

In response to the strikes, a spokesperson for the Iranian Mission for the U.N. said late Sunday, "Iran has nothing to do with the attacks in questions. The conflict has been initiated by the United States military against resistance groups in Iraq and Syria; and such operations are reciprocal between them."

Secretary of Defense Lloyd Austin lamented the attack in his own statement, promising that "the president and I will not tolerate attacks on American forces, and we will take all necessary actions to defend the United States, our troops, and our interests."

CENTCOM initially said 25 troops were injured in the attack by a one-way drone, also known as a "suicide" drone. The number of injured later increased to at least 40, officials said. and then to at least 34. At least eight were evacuated for high-level treatment.

Some of the injured service members received serious wounds from shrapnel and some were being screened for traumatic brain injuries, an official with the White House National Security Council said.

The three slain service members were not immediately identified, pending notification of their families, according to U.S. Central Command, which released a short statement on Sunday confirming the incident.

The strike occurred at the Tower 22 outpost, an administration official said.

CENTCOM initially said 25 troops were injured in the attack by a one-way drone, also known as a "suicide" drone. The number of injured later increased to at least 30, according to a defense official, and then to at least 34, CENTCOM said in a subsequent statement. Eight of the injured were evacuated for a higher level of care but were in stable condition.

Some of the injured service members received serious wounds from shrapnel and some were being screened for traumatic brain injuries, an official with the White House National Security Council said. The number of injured could change, this official said.

Biden was briefed multiple times in the hours after the strike and said in his statement on Sunday that the U.S. was "still gathering the facts" surrounding the "wholly unjust attack," which he said occurred Saturday night.

The White House clarified that the attack occurred early Sunday in Jordan, or late Saturday Eastern time.

The president in his statement on Sunday hailed the killed service members for being "unwavering in their bravery. Unflinching in their duty. Unbending in their commitment to our country."

Located in the northeastern region of Jordan, the Tower 22 is a small outpost that supports operations across the border at the U.S. base at al-Tanf in Syria and contributes to the Pentagon's advise-and-assist mission for the Jordanian military.

Iran-backed militias have in recent months carried out more than a hundred attacks in the region, primarily on U.S. troops stationed in Iraq and Syria but also on American ships and international commercial vessels in the Red Sea and the Gulf of Aden.

The strikes have wounded scores of American troops, including one who sustained a serious injury on Christmas Day in an attack on the Erbil air base in Iraq.

Two Navy SEALS were also presumed dead after they were lost at sea during a mission that successfully intercepted a vessel carrying Iranian-made missile parts destined for Yemen.

U.S. forces began conducting targeted, retaliatory strikes on fighters in the Middle East in October, which the Pentagon has consistently described as defensive measures intended to degrade the militias' proficiency and deter them from escalating.

After months of attacks primarily targeting commercial vessels in the waters surrounding Yemen, the U.S. also launched a number of strikes against the country's Houthi rebels in January.

U.S. officials initially expressed hope that carrying out operations in the two theaters would diminish the belligerent groups' capabilities for further conflict, but the tit-for-tat exchanges with militants in Syria, Iraq and Yemen have instead steadily escalated.

That protracted pattern has fueled questions about the broader military strategy.

"What do they [critics of the current approach] want? A broader conflict? Do you want us in a full-scale war?" Gen. CQ Brown Jr., the chairman of the Joint Chiefs of Staff, said in a recent interview with ABC News Chief Global Affairs Correspondent Martha Raddatz.

Some lawmakers have also criticized the White House for not first seeking authorization from Congress for the Yemen strikes, though the administration maintains it acted under existing legal authority to carry out such operations.

In the hours after the Jordan strike was confirmed, a growing number of members of Congress spoke out. Many of them offered condolences to the slain and wounded service members, and Republicans argued that the Biden administration had failed to adequately address Iran.

"We need a major reset of our Middle East policy to protect our national security interests and restore deterrence," House Foreign Affairs Committee Chairman Michael McCaul said in a statement as House Speaker Mike Johnson called for "a crystal clear message across the globe that attacks on our troops will not be tolerated."

In the interview taped last week with Martha Raddatz, Gen. Brown was asked if Americans being killed in the Middle East would impact his decision making.

He said the military was doing "everything we can to protect our forces" and noted the U.S. does not want "broader conflict" in the region -- and that he doesn't believe Iran wants war with the U.S., either.

"We don't want to go down a path of greater escalation that drives to a much broader conflict within the region," Brown said.

Before the start of the Israeli-Hamas war, U.S. forces in the Middle East experienced a two-year period of relative calm.

The last major attack to result in multiple American service members killed in action was the bombing outside of the Kabul, Afghanistan, airport in August 2021, which claimed the lives of 13 U.S. troops and more than 180 Afghan citizens.

ABC News' Will Gretsky, Mariam Khan, Meghan Mistry, Lauren Peller, Martha Raddatz, Fritz Farrow and MaryAlice Parks contributed to this report.