WASHINGTON (AP) — The United States on Wednesday attributed the drone attack that killed three U.S. service members in Jordan to the Islamic Resistance in Iraq, an umbrella group of Iran-backed militias, as President Joe Biden weighs his options to respond to the strike.

Iran threatened to "decisively respond" to any U.S. attack on the Islamic Republic after the U.S. said it held Tehran responsible. The U.S. has signaled it is preparing for retaliatory strikes in the Mideast in the wake of the Sunday drone attack that also wounded more than 40 troops at Tower 22, a secretive base in northeastern Jordan that's been crucial to the American presence in neighboring Syria.

National Security Council spokesman John Kirby said Wednesday the U.S. believes the attack was planned, resourced and facilitated by the Islamic Resistance in Iraq, an umbrella group that includes the militant group Kataib Hezbollah. He said Biden "believes that it is important to respond in an appropriate way."

He said Biden was continuing to weigh his options, but Kirby said "the first thing you see won't be the last thing," adding it "won't be a one-off."

Kirby dismissed a statement by Iraqi militia Kataib Hezbollah announcing "the suspension of military and security operations against the occupation forces in order to prevent embarrassment to the Iraqi government." He said the group can't be taken at face value, and he added, "they're not the only group that has been attacking us."

As of Wednesday, Kataib Hezbollah and other Iran-aligned militias had launched 166 attacks on U.S. military installations since Oct. 18, including 67 in Iraq, 98 in Syria and the one in Jordan, according to the U.S. military.

The U.S. has struck back at the militias a few times over the past three months. On Oct. 27, U.S. fighter jets struck two weapons and ammunition storage sites in eastern Syria near Boukamal that were used by Iran's Islamic Revolutionary Guard Corps and Iranian-backed groups.

Also in Syria, fighter jets dropped bombs on an IRGC weapons storage facility near Maysulun in Deir el-Zour on Nov. 8. And U.S. airstrikes targeted a training facility and a safe house in the Bulbul district of Mayadin on Nov. 12.

On Dec. 26, the U.S. launched strikes on three locations in Iraq used by Kataib Hezbollah and affiliated groups, and on Jan. 23, the U.S. struck three sites in Iraq, again targeting Kataib Hezbollah.

Any additional American strikes could further inflame a region already roiled by Israel's ongoing war on Hamas in the Gaza Strip. The war began with Hamas attacking Israel on Oct. 7, killing some 1,200 people and taking about 250 hostage. Since then, Israeli strikes have killed more than 26,000 Palestinians and displaced nearly 2 million others from their homes, arousing anger throughout the Muslim world.

Violence has erupted across the Mideast, with Iran striking targets in Iraq, Pakistan and Syria, and the U.S. carrying out airstrikes targeting Yemen's Iran-backed Houthi rebels over their attacks on shipping in the Red Sea. Some observers fear a new round of strikes targeting Iran could tip the region into a wider war.

A U.S. official, speaking on condition of anonymity to discuss military operations, said American F/A-18 fighter jets on Wednesday struck and destroyed 10 Houthi drones that were prepared to launch.

The U.S. military's Central Command said later Wednesday that the guided missile destroyer USS Carney had shot down one anti-ship ballistic missile fired from Houthi-controlled areas of Yemen toward the Gulf of Aden. The Carney also shot down three Iranian drones, Central Command said.

The Iranian warnings first came from Amir Saeid Iravani, Iran's ambassador to the United Nations in New York. He gave a briefing to Iranian journalists late Tuesday, according to the state-run IRNA news agency.

"The Islamic Republic would decisively respond to any attack on the county, its interests and nationals under any pretexts," IRNA quoted Iravani as saying. He described any possible Iranian retaliation as a "strong response," without elaborating.

The Iranian mission to the U.N. did not respond to requests for comment or elaboration Wednesday on Iravani's remarks.

Iravani also denied that Iran and the U.S. had exchanged any messages over the last few days, either through intermediaries or directly. The pan-Arab satellite channel Al Jazeera, which is based in and funded by Qatar, reported earlier that such communication had taken place. Qatar often serves as an intermediary between Washington and Tehran.

But Iran's government has taken note of the U.S. threats of retaliation for the attack on the base in Jordan.

"Sometime, our enemies raise the threat, and nowadays we hear some threats in between words by American officials," Revolutionary Guard commander Gen. Hossein Salami, who answers only to Supreme Leader Ayatollah Ali Khamenei, said at an event Wednesday. "We tell them that you have experienced us, and we know each other. We do not leave any threat without an answer."

"We are not after war, but we have no fear of war," he added, according to IRNA.

Kirby, for his part, said the U.S. doesn't "seek a war with Iran. We're not looking for a broader conflict."

On Saturday, a general in charge of Iran's air defenses described them as being at their "highest defensive readiness." That raises concerns for commercial aviation traveling through and over Iran as well. After a U.S. drone strike killed a top general in 2020, Iranian air defenses mistakenly shot down a Ukrainian passenger plane, killing all 176 people on board.

Meanwhile, attacks by the Houthis and counterattacks by the U.S. continue in the Red Sea.

The private security firm Ambrey reported Wednesday night that a ship was targeted with a missile southwest of Aden, Yemen, near the Bab el-Mandeb Strait between the Red Sea and the Gulf of Aden. The Houthis claimed an attack on a vessel at the time called the Koi, a Liberian-flagged container ship. The ship's managers could not be immediately reached for comment. It was unclear if the reported missile attack caused any damage or injuries.

A missile launched Tuesday night targeted the USS Gravely, a guided missile destroyer, Central Command said in a statement. No injuries or damage were reported.

A Houthi military spokesman, Brig. Gen. Yahya Saree, claimed responsibility for the attack in a statement Wednesday morning, calling it "a victory for the oppression of the Palestinian people and a response to the American-British aggression against our country."

Saree claimed the Houthis fired "several" missiles, something not acknowledged by the U.S. Navy. Houthi claims have been exaggerated in the past, and their missiles sometimes crash on land and fail to reach their targets.

Since November, the rebels have repeatedly targeted ships in the Red Sea over Israel's offensive against Hamas in Gaza. But they have frequently targeted vessels with tenuous or no clear links to Israel, imperiling shipping in a key route for global trade between Asia, the Mideast and Europe.

The Houthis hit a commercial vessel with a missile on Friday, sparking a fire that burned for hours.

The U.S. and the United Kingdom have launched multiple rounds of airstrikes targeting the Houthis as allied warships patrol the waterways affected by the attacks. The European Union also plans to launch a naval mission in the Red Sea within three weeks to help defend cargo ships against the Houthi attacks, the bloc's top diplomat said Wednesday.

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Associated Press writers Nasser Karimi in Tehran, Iran, and Tara Copp and Lolita C. Baldor in Washington contributed to this report.