WASHINGTON

The US formally attributed blame for a deadly suicide drone attack Wednesday that killed three American troops in Jordan to an umbrella organization of Iranian-backed militias.

National Security Council spokesperson John Kirby told reporters that the US intelligence community has determined that the Islamic Resistance in Iraq helped to plan, resource and facilitate Sunday's attack. While he stopped short of blaming any one militia, he said it "certainly has the earmarks of" the types of attacks conducted by Kataib Hezbollah.

"The attribution that our intelligence community is comfortable with is that this was done by the umbrella group that is called the Islamic resistance in Iraq," Kirby told reporters at the White House.

Sunday's suicide drone attack killed three American troops and injured at least 34 others at Tower 22, a remote military installation in Jordan near the Syrian and Iraqi borders. An umbrella group of Iranian-backed militias calling itself the Islamic Resistance in Iraq claimed responsibility.

The group has been carrying out drone and missile attacks on US forces in the region for months amid Israel's ongoing war against the besieged Gaza Strip. Sunday's fatalities were the first to have resulted from the attacks. Most others were intercepted or resulted in minor injuries to American forces.

US President Joe Biden said Tuesday that he has determined how he will respond to Sunday's drone attack, but did not offer details on what it will entail.

While he has emphasized that he is not seeking to create "a wider war in the Middle East," he said he holds Iran responsible "in the sense that they're supplying weapons to the people who did it."

Iran vowed Wednesday to decisively respond to any attack that targets its territories or interests, following Washington's threats.

A statement issued by Iran's permanent mission to the UN warned that Tehran would respond decisively to any attack on its territory, interests or nationals outside its borders, according to the official Iranian IRNA agency.

It also denied reports about the US sending messages to Iran via mediators in the past two days.