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US President Joe Biden was facing political pressure on Sunday to strike Iran-supported militias, and even Iran itself, after a drone attack killed three US troops in Jordan and wounded dozens more.
The Tehran-backed strike on an American military outpost near the Jordan-Syria border is expected to stoke tension in the region, amid recent US strikes on Houthi rebels in Yemen who have been attacking commercial and military ships in the Red Sea in what they claim to be response to Israel's war in Gaza.
“Have no doubt – we will hold all those responsible to account at a time and in a manner of our choosing,” Mr Biden said.
“While we are still gathering the facts of this attack, we know it was carried out by radical Iran-backed militant groups operating in Syria and Iraq.”
Wounded personnel were being evacuated from Jordan's US base for further treatment, Reuters reported.
It was the first time American military personnel have been killed in hostile fire since the start of the Israel-Gaza war on October 7.
The Jordanian government initially denied that the attack had occurred on the Jordanian side, but said in a statement on Sunday that it had occurred in “an advanced position on the border with Syria”.
Amman condemned the “terrorist attack”, saying it was working with Washington to fight terrorism.
The White House said that Mr Biden, who is on a campaign visit in South Carolina, was briefed on the attack by Defence Secretary Lloyd Austin and other top officials.
“I am outraged and deeply saddened by the deaths of three of our US service members and the wounding of other American troops in an attack last night against US and coalition forces, who were deployed to a site in north-eastern Jordan near the Syrian border to work for the lasting defeat of ISIS,” Mr Austin said.
“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,” he said.
Republican opponents of Mr Biden seized on the attack as evidence of his failure to confront Iran as its proxies strike against US forces across the region.
“The only answer to these attacks must be devastating military retaliation against Iran’s terrorist forces … Anything less will confirm Joe Biden as a coward,” Republican Senator Tom Cotton said.
Few easy options
The Biden administration has been seeking to contain the war on Gaza as part of efforts to avoid a wider regional conflict, even as the US continues to conduct retaliatory strikes on Houthis in the Red Sea.
“Part of our work here is to make sure, as things have happened in the Middle East, is not to have the conflict broaden,” Gen Charles Brown, the US chairman of the Joint Chiefs of Staff, said on Sunday in a recorded interview on ABC.
“We want to ensure that we take away capability while we protect our forces and at the same time not have this broaden into a much wider conflict.”
The US Central Command said: “On January 28, three US service members were killed and 25 injured from a one-way attack [drone] that impacted at a base in north-east Jordan, near the Syria border.”
US media reported that the attack occurred near Tower 22 in Jordan, a small US base in the north-eastern desert corner of the kingdom, on the border with Iraq and Syria.
It is also a few kilometres away from Syria's Al Tanf Garrison, another US base at the junction of the borders of Syria, Iraq and Jordan.
The outpost has been the target of Iranian-backed proxies several times since October.
The attack is likely to bring domestic pressure on Mr Biden, who is running for re-election in November.
The US House of Representatives' foreign affairs committee on Sunday criticised the Biden administration's “failed Middle East policy”, which it said “has destroyed our deterrence against adversaries” in the region.
“We need a major reset of our Middle East policy to protect our national security interests and restore deterrence,” committee chairman Mike McCaul, a Republican, said on Sunday.
Hawkish Republican senator Lindsey Graham went further, calling on the US to “strike targets of significance inside Iran” and to “hit them hard”.
Jordan has a defence pact with the US and has several thousand American troops stationed in the country.
The US also has played a major role in fortifying the kingdom's border with Syria, where the Lebanese militant group Hezbollah and other militias supported by Iran operate.
Mr Biden called the attack “despicable and wholly unjust”, and said the US service members were “risking their own safety for the safety of their fellow Americans, and our allies and partners with whom we stand in the fight against terrorism. It is a fight we will not cease”.
British Foreign Secretary David Cameron condemned the attacks, saying in a post on X, formerly Twitter, that “we strongly condemn attacks by Iran-aligned militia groups against US forces. We continue to urge Iran to de-escalate in the region”.
