WASHINGTON ― The Pentagon’s announcement that that U.S. forces conducted deadly airstrikes in Syria sparked complaints from some of President Joe Biden’s Democratic allies that he overreached, while key Republicans applauded the move.

The reactions came after the Feb. 25 airstrikes targeted facilities belonging to an Iranian-backed Iraqi armed group, reportedly killing one fighter. The Pentagon said the strikes were retaliation for a rocket attack in Iraq earlier this month that killed one civilian contractor and wounded a U.S. service member and other coalition troops.

The strike could be a test of whether Congress, which fought to reclaim its war-making powers under President Donald Trump, will continue that fight under Biden. The reactions are also a sign of potential fault lines with progressives, who have been able to make inroads and sway Biden on some foreign policy matters, especially to rein in the military’s involvement in the Middle East.

Sen. Tim Kaine, D-Va., who led efforts to repeal the 2001 and 2002 authorizations for the use of military force, called on the Biden administration to brief Congress on the strike and justify why he did not first seek approval from the legislative branch.

“Offensive military action without congressional approval is not constitutional absent extraordinary circumstances. Congress must be fully briefed on this matter expeditiously,” said Kaine, a member of the Armed Services and Foreign Relations committees.

Sen. Chris Murphy, D-Conn., noted that the president has the right to defend the nation and its armed forces from imminent attack, but called the recent airstrikes in Syria “unacceptable.”

“I have inherent trust in the national security decision-making of President Biden, and I know how seriously he takes Congress’ war-making powers,” said Murphy, a Foreign Relations Committee member. “But Congress should hold this administration to the same standard it did prior administrations, and require clear legal justifications for military action, especially inside theaters like Syria, where Congress has not explicitly authorized any American military action.”

Several libertarian Republicans joined in the backlash.

“I condemn meddling in Syria’s civil war,” Kentucky Republican Sen. Rand Paul said in a tweet. “I also condemn attacking a sovereign nation without authority. What authority does [Biden] have to strike Syria?”

The Biden administration in its first weeks emphasized its intent to focus more on the challenges posed by China, even as Mideast threats persist. Biden’s decision to attack in Syria did not appear to signal an intention to widen U.S. military involvement in the region but rather to demonstrate a will to defend U.S. troops in Iraq and send a message to Iran.

Defense Secretary Lloyd Austin said he is “confident” the U.S. hit back at the “same Shia militants that conducted the strikes,” referring to the fatal Feb. 15 rocket attack in northern Iraq.

Earlier, Pentagon spokesman John Kirby said the U.S. airstrikes send “an unambiguous message: President Biden will act to protect American and coalition personnel.” The strikes “destroyed multiple facilities at a border control point used by a number of Iranian-backed militant groups,” he said.

Lead Republicans and some Democrats quickly praised the operation, saying it sent a strong message to Iran and could deter its proxies from future violent acts against American troops.

“Today’s airstrike demonstrates President Biden’s resolve to prevent Iran from targeting America’s personnel and allies with impunity,” said House Majority Leader Steny Hoyer, D-Md. “It was a strong act that will surely send a message to Tehran that our country will not abide destabilizing actions from its forces or its proxies.”

House Armed Services Committee Chairman Adam Smith, D-Wash., voiced strong, but measured support.

“While the military strike was necessary to protect our personnel in the region and deter further attacks,” he said, “I have spoken with the Biden administration’s national security team and they are committed to using diplomacy and engagement with Iran, and also working with our allies and partners in the region to deescalate tensions going forward. I strongly support this effort.”

House Armed Services Committee ranking member Mike Rogers, R-Ala., and his Senate counterpart Jim Inhofe, R-Okla., also voiced support. Inhofe called the airstrikes correct and proportionate, but also threw in barbed criticism of Biden’s efforts to renegotiate the Iran nuclear deal.

“The fact that Iran chose to escalate shortly after the administration declared its desire to resume negotiations with Tehran has not gone unnoticed,” Inhofe said in a statement. “I hope the administration rethinks its current negotiating strategy with Iran and works with Congress on a bipartisan approach.”

Progressives and some of the antiwar groups they worked with to secure Biden’s commitment to end U.S. support for offensive military operations in Yemen by Saudi Arabia and the United Arab Emirates expressed dismay on Friday.

“We need to extricate from the Middle East, not escalate,” Rep. Ro Khanna, D-Calif., said in a statement Friday. “The president should not be taking these actions without seeking explicit authorization instead of relying on broad, outdated [authorizations]. I spoke against endless war [under] Trump, and I will speak out against it when we have a Democratic President.”

The Associated Press contributed to this report.