WASHINGTON (AP) -- President Joe Biden on Tuesday indicated he had decided how to respond after the killing of three American service members Sunday in a drone attack in Jordan that his administration has pinned on Iran-backed militia groups, saying he does not want to expand the war in the Middle East but demurring on specifics.

U.S. officials said they are still determining which of several Iran-backed groups was responsible for the first killing of American troops in a wave of attacks against U.S. forces in the region since the Oct. 7 Hamas assault on Israel. Biden plans to attend the dignified transfer to mark the fallen troops' return to American soil on Friday and answered in the affirmative when asked by reporters if he'd decided on a response, as he indicated he was aiming to prevent further escalation.

"I don't think we need a wider war in the Middle East," Biden said at the White House before departing for a fundraising trip to Florida. "That's not what I'm looking for."

It was not immediately clear whether Biden meant he had decided on a specific retaliatory plan. A U.S. official told The Associated Press that the Pentagon is still assessing options to respond to the attack in Jordan.

National Security Council spokesman John Kirby told reporters traveling with Biden aboard Air Force One that he would not preview the U.S. response, but indicated it would come in phases.

"It's very possible that what you'll see is a tiered approach here, not just a single action, but potentially multiple actions over a period of time," he said.

Meanwhile, the Iranian-backed Iraqi militia Kataib Hezbollah, one of several groups eyed by U.S. officials, announced Tuesday in a statement "the suspension of military and security operations against the occupation forces in order to prevent embarrassment to the Iraqi government."

The attacks on U.S. forces by Iraqi militias over the past four months have placed the government of Iraqi Prime Minister Mohammed Shia al-Sudani in an awkward position. Sudani was brought to power by Iranian-allied factions but has also attempted to stay in Washington's good graces and has condemned the attacks on U.S. forces serving in Iraq as part of an international commission to fight the Islamic State. Iraqi and U.S. officials on Saturday opened talks aimed at winding down the commission's presence.

Kirby said that Biden spoke with the soldiers' families Tuesday morning and extended his condolences, pledging full assistance to the families as they grieve.

In separate calls with the families, Biden also gauged their feelings about his attendance at Friday's dignified transfer of the fallen service members' remains at Dover Air Force Base in Delaware on Friday, and "all of them supported his presence there," Kirby said.

"He was grateful for their time. He expressed to them how proud we all are of their service," Kirby said of Biden's calls with the families. "How we mourn and feel sorrow over their loss."

Kirby added: "The president will be going to the dignified transfer on Friday."

The solemn ceremony marks the return of fallen service members to American soil as they journey to their final resting place, with silent honor guards carrying flag-draped transfer cases holding the remains from transport aircraft to military vehicles.

The Pentagon identified those killed in the attack 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. The Army Reserve announced on Tuesday that it had posthumously promoted Sanders and Moffett to the rank of sergeant.

The three U.S. Army Reserve soldiers were assigned to the 718th Engineer Company, 926th Engineer Battalion, 926th Engineer Brigade in Fort Moore, Georgia.

There have been a total of 166 attacks on U.S. military installations since Oct. 18, including 67 in Iraq, 98 in Syria and now one in Jordan, a U.S. military official said. On Tuesday, Al-Asad Air Base in Western Iraq was targeted again by a single rocket, but there was no damage and no injuries in that attack, a U.S. military official said. The three soldiers killed in the Jordan strike were the first U.S. military fatalities in the Middle East since the war between Israel and Hamas broke out. One contractor has also died as the result of a heart attack after a strike on Al-Asad in December.

In 2021, Biden attended the dignified transfer of the remains of 13 troops killed in a suicide attack during the U.S. withdrawal from Afghanistan.

Meanwhile, U.S. forces may have mistaken an enemy drone for an American one and let it pass unchallenged into the desert base in Jordan where it killed three U.S. troops and wounded dozens more, officials said Monday.

As the enemy drone was flying in at a low altitude, a U.S. drone was returning to the small installation known as Tower 22, according to a preliminary report cited by two officials, who were not authorized to comment and insisted on anonymity,
As a result, there was no effort to shoot down the enemy drone that hit the outpost. One of the trailers where troops sleep sustained the brunt of the strike, while surrounding trailers got limited damage from the blast and flying debris. While there are no large air defense systems at Tower 22, the base does have counter-drone systems, such as Coyote drone interceptors.

Aside from the soldiers killed, the Pentagon said more than 40 troops were wounded in the attack, most with cuts, bruises, brain injuries and similar wounds. Eight were medically evacuated, including three who were going to Landstuhl Regional Medical Center in Germany. The other five, who suffered "minor traumatic brain injuries," were expected to return to duty.

Asked if the failure to shoot down the enemy drone was "human error," Pentagon spokeswoman Sabrina Singh responded that the U.S. Central Command was still assessing the matter.

The explanation for how the enemy drone evaded U.S. air defenses came as the White House said Monday it's not looking for war with Iran even as Biden vows retaliatory action. The Democratic administration believes Tehran was behind the strike.

"There's no easy answer here," said Kirby. "And that's why the president is meeting with his national security team weighing the options before him."

The brazen attack, which the Biden administration blames on Iranian-based proxies, adds another layer of complexity to an already tense Mideast situation as the Biden administration tries to keep the Israel-Hamas war from expanding into a broader regional conflict.

"The president and I will not tolerate attacks on U.S. forces, and we will take all necessary actions to defend the U.S. and our troops," Defense Secretary Lloyd Austin said as he met at the Pentagon with NATO Secretary General Jens Stoltenberg.

Biden promised on Sunday to "hold all those responsible to account at a time and in a manner (of) our choosing" but said the U.S. wasn't seeking to get into another conflict in the Middle East.

Kirby also made clear that American patience has worn thin after more than two months of attacks by Iranian proxies on U.S. troops in Iraq, Syria and Jordan and on U.S. Navy and commercial vessels in the Red Sea. The proxy groups — including Yemen's Houthi rebels and Iraq-based Kataeb Hezbollah — say the attacks are in response to Israel's ongoing military operations in Gaza.

"We are not looking for a war with Iran," Kirby told reporters. "That said, this was a very serious attack. It had lethal consequences. We will respond, and we respond appropriately."

Iran on Monday denied it was behind the Jordan strike.

"These claims are made with specific political goals to reverse the realities of the region," Iran's state-run IRNA news agency quoted foreign ministry spokesman Nasser Kanaani as saying. Iran regularly denies involvement in attacks linked back to it through the militias it arms across the wider Mideast.

Kirby said that U.S. officials are still working through determining which militant group was behind the attack. He noted that Iran has longed equipped and trained the militias.

Republicans have laid blame on Biden for doing too little to deter Iranian militias, which have carried out approximately 165 attacks on U.S. troops in the region since the start of the war.

Republican presidential front-runner Donald Trump on Sunday called the attack "yet another horrific and tragic consequence of Joe Biden's weakness and surrender."

The attack hit a U.S. military desert outpost in the far reaches of northeastern Jordan known as Tower 22. The installation sits near the demilitarized zone on the border between Jordan and Syria along a sandy, bulldozed berm marking the DMZ's southern edge. The Iraqi border is only 10 kilometers (6 miles) away.

The base began as a Jordanian outpost watching the border, then saw an increased U.S. presence after American forces entered Syria in late 2015. The small installation includes U.S. engineering, aviation, logistics and security troops, with about 350 U.S. Army and Air Force personnel deployed.

Iraq's government condemned the drone strike. Spokesman Bassem al-Awadi said in a statement that Iraq was "monitoring with a great concern the alarming security developments in the region" and called for "an end to the cycle of violence." The statement said that Iraq is ready to participate in diplomatic efforts to prevent further escalation.

An umbrella group for Iran-backed factions known as the Islamic Resistance in Iraq has claimed dozens of attacks against bases housing U.S. troops in Iraq and Syria since the Israel-Hamas war began. On Sunday, the group claimed three drone attacks against sites in Syria, including near the border with Jordan, and one inside of "occupied Palestine" but so far hasn't claimed the attack in Jordan.

John Bolton, who served as national security adviser to Trump, said Iran hasn't paid a price for the havoc that its proxies have unleashed in the region. He suggested the Biden administration could send a strong message to Tehran with strikes on Iranian vessels in the Red Sea, Iranian air defenses along the Iraqi border, and bases that have been used to train and supply militant groups for years.

"So until Iran bears a cost, you're not going to reestablish deterrence, you're not going to put the belligerence on a downward slope."

The attack came as U.S. officials were seeing signs of progress in negotiations to broker a deal between Israel and Hamas to release the more than 100 remaining hostages being held in Gaza in exchange for an extended pause in fighting. While contours of a deal under consideration would not end the war, Americans believed that it could lay the groundwork for a durable resolution to the conflict.

Qatar's prime minister said Monday that senior U.S. and Mideast mediators had achieved a framework proposal to present to Hamas for freeing hostages and pausing fighting in Gaza.

Prime Minister Mohammed al-Thani's comments at the Atlantic Council in Washington came after talks Sunday in Paris among U.S., Israeli, Qatari and Egyptian officials seeking a new round of hostage releases and a cease-fire in Gaza.

Associated Press writers Qassim Abdul-Zahra in Baghdad, Jon Gambrell in Jerusalem and Geir Moulson in Berlin contributed reporting. Madhani reported from Jupiter, Fla. AP writers Lolita C. Baldor and Tara Copp in Washington and Abby Sewell in Beirut contributed.