President Joe Biden said Friday that Iran should view his decision to authorize US airstrikes in Syria as a warning that it can expect consequences for its support of militia groups that threaten US interests or personnel.

“You can’t act with impunity. Be careful,” Biden said when a reporter asked what message he had intended to send with the airstrikes, which the Pentagon said destroyed several buildings in eastern Syria but were not intended to eradicate the militia groups that used them to facilitate attacks inside Iraq.

Administration officials defended the Thursday night airstrikes as legal and appropriate, saying they took out facilities that housed valuable “capabilities” used by Iranian-backed militia groups to attack American and allied forces in Iraq.

John Kirby, the Pentagon’s chief spokesperson, said members of Congress were notified before the strikes as two Air Force F-15E aircraft launched seven missiles, destroying nine facilities and heavily damaging two others, rendering both “functionally destroyed.” He said the facilities, at “entry control points” on the border, had been used by militia groups the US deems responsible for recent attacks against US interests in Iraq.

In a political twist for the new Democratic administration, several leading Congress members in Biden’s own party denounced the strikes, which were the first military actions he authorized.

Democrats said the airstrikes were done without authorization from lawmakers, while Republicans were more supportive.

“Offensive military action without congressional approval is not constitutional absent extraordinary circumstances,” said Sen. Tim Kaine, D-Va. And Sen. Chris Murphy, D-Conn., said lawmakers must hold the current administration to the same standards as any other. “Retaliatory strikes not necessary to prevent an imminent threat,” he said, must get congressional authorization.

But Sen. Jim Inhofe of Oklahoma, the ranking Republican on the Senate Armed Services Committee, backed the decision as “the correct, proportionate response to protect American lives.”

White House press secretary Jen Psaki told reporters Friday that Biden used his constitutional authority to defend US personnel.

“The targets were chosen to correspond to the recent attacks on facilities and to deter the risk of additional attacks over the coming weeks,” she said. Among the recent attacks cited was a Feb. 15 rocket attack in northern Iraq that killed one civilian contractor and wounded a US service member and other coalition troops.