Iran said it had nothing to do with the attack and denied US and British accusations that it supported militant groups responsible for the strike on the remote frontier base in Jordan's northeast, near the borders with Iraq and Syria.
"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," Biden said in a statement, pledging to hold "all those responsible to account at a time and in a manner of our choosing."
Biden later held a moment of silence at a South Carolina church banquet hall for the US troops killed in the attack, vowing: "We shall respond."
With the region already tense as fighting rages in Gaza, the strike will also raise fears of a broader conflict directly involving Tehran.
There has so far been no claim of responsibility for the strike but British Foreign Secretary David Cameron reiterated a call for Iran "to de-escalate in the region."
He also condemned the attack "by Iran-aligned militia groups" in a post on social media platform X.
Iranian representatives at the United Nations told the official IRNA news agency Tehran had nothing to do with the attack. A foreign ministry spokesman also rejected the US and British accusations.
"These claims are made with specific political goals to reverse the realities of the region," IRNA quoted foreign ministry spokesman Nasser Kanaani as saying.
Iran executed four men at dawn on Monday after they were convicted of spying for Israel, the judiciary's website Mizan Online reported.
'Regional explosion'
Hamas spokesman Sami Abu Zuhri said the Jordan attack was "a message to the American administration."
"The continuation of the American-Zionist aggression on Gaza risks a regional explosion," Abu Zuhri said.
The US Central Command (CENTCOM) said late on Sunday the attack had hit the remote Tower 22 logistics support base and that 34 personnel were also wounded, eight of whom required evacuation.
There are around 350 US Army and Air Force personnel at the base who operate in support roles, including for the international coalition against the Islamic State jihadist group, CENTCOM said.
Jordan's government spokesman Muhannad Mubaidin condemned the attack, as did Bahrain and Egypt.
The escalating Middle East conflict poses a challenge to Biden in an election year.
Republican politicians were quick to take aim at Biden over the deadly attack, including his predecessor Donald Trump, who described the situation as a "consequence of Joe Biden's weakness and surrender."
US and allied forces in Iraq and Syria have been targeted in more than 150 attacks since mid-October, according to the Pentagon, and Washington has carried out retaliatory strikes in both countries.
Many of the attacks on US personnel have been claimed by the Islamic Resistance in Iraq, a loose alliance of Iran-linked armed groups that oppose US support for Israel in the Gaza conflict.
The latest round of the Israel-Hamas conflict began when the Palestinian militant group carried out an unprecedented attack on October 7 that resulted in about 1,140 deaths, mostly civilians, according to an AFP tally of official figures.
Israel retaliated with a relentless military offensive that has killed at least 26,422 people in Gaza, most of them women and children, according to the Gaza health ministry.
Anger over that campaign has grown across the region, with violence involving Iran-backed groups in Lebanon, Iraq and Syria as well as Yemen.
There have been near-daily exchanges of fire between Hezbollah and Israel in Lebanon. US forces are directly involved in Iraq, Syria and Yemen.
The United States and Britain have both carried out strikes targeting Yemen's Iran-backed Huthi rebels, who have been attacking Red Sea shipping in support of Palestinians in Gaza for more than two months.
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