WASHINGTON — The US has determined the Islamic Resistance in Iraq (IRI) was responsible for the weekend drone attack that killed three American soldiers in Jordan, National Security Council spokesman John Kirby said Wednesday as the Biden administration readies retaliatory strikes.

The IRI is an umbrella organization of Iranian proxy militias, including Kataib Hezbollah, that have also been involved in carrying out at least 165 strikes against US and coalition forces in Iraq and Syria since Oct. 17.

President Biden vowed this week to retaliate for the Saturday strike, which represented the first time American troops were killed by hostile fire in the region-wide conflict that began with the Oct. 7 Hamas terror attack against Israel.

As critics complain the US has not acted fast enough in striking back at those responisible for the troop deaths, Kirby cautioned that “just because you haven’t seen anything in the last 48 hours, doesn’t mean that you’re not going to see anything.”

The spokesman added that the administration’s response may be multifaceted and involve a series of attacks rather than one concise strike.

“I would also caution you not to think that the first thing you see (will) be the last,” Kirby said.

The response is not expected to include assistance from other nations that make up the coalition forces in the region.

“We’re focusing on a US response,” Kirby said. “They killed American troops.”

In addition to the three killed Saturday, more than 80 US troops have been injured in the recent spate of Tehran-backed attacks across the Middle East, according to the Pentagon.

Katib Hezbollah announced Tuesday it would cease its attacks on American forces in the region, but Kirby said words would not be enough to deter the US from following through with counterstrikes.

Pentagon spokesman Air Force Brig. Gen. Pat Ryder said Tuesday it was still unknown whether Hezbollah would follow through with its pledge.

“Actions speak louder than words,” he said.