President Biden said Monday that he acted within his constitutional authority to order what his administration calls retaliatory airstrikes against Iran-linked targets in Iraq and Syria, which came as the White House has backed efforts to rewrite congressional authorization for such actions.

The strikes also came as nuclear negotiations with Iran appear at an impasse.

“I directed last night’s airstrikes, targeting sites used by the Iranian-backed militia group responsible for recent attacks on U.S. personnel in Iraq, and I have that authority under Article II — and even those up on the Hill who are reluctant to acknowledge that have acknowledged that is the case,” Biden said.

The airstrikes Sunday evening led to warnings from some Democrats that Biden risked flouting the constitutional requirement to consult Congress. Sen. Chris Murphy (D-Conn.), a Biden ally and senior member of the Foreign Relations Committee, was blunt in his concern.

“There is no doubt that President Biden possesses the ability to defend our forces abroad, and I continue to trust inherently the national security instincts of this White House,” Murphy said in a statement issued late Sunday.

“My concern is that the pace of activity directed at U.S. forces and the repeated retaliatory strikes against Iranian proxy forces are starting to look like what would qualify as a pattern of hostilities under the War Powers Act. Both the Constitution and the War Powers Act require the president to come to Congress for a war declaration under these circumstances.”

Biden cited his authority under Article II of the Constitution, which allows him to act on behalf of U.S. military service members in self-defense, for the strikes Sunday and an earlier set in February.

The White House supports an effort in Congress to repeal the emergency authorization of force approved after the terrorist attacks of Sept. 11, 2001. That authorization has been used ever since as justification for the wars in Afghanistan and Iraq as well as other military actions.

“The United States selected these targets because Iran-backed militias used them to conduct at least five [drone] attacks against U.S. facilities in Iraq since April,” White House press secretary Jen Psaki told reporters Monday.

The White House maintains that the action abides by domestic and international law.

“The president has been clear that there will be serious consequences if Iranian leaders continue to arm, fund and train militia groups to attack our people,” Psaki said.

Pentagon spokesman John Kirby said two Iranian-linked militia locations in Syria were attacked, along with one in Iraq, and described the strikes as defensive. The locations were used by the Kataib Hezbollah and Kataib Sayyid al-Shuhada groups, which both have ties to Iran. Kataib Sayyid al-Shuhada said four of its militiamen were killed.

Iraq condemned the U.S. airstrike on its soil Monday, describing the overnight attack as a “blatant” violation of national sovereignty that breached international conventions.

The White House sidestepped the unusually harsh condemnation from a military ally.

“The prime minister is a partner. He has a tough job,” Psaki said. “His statement calls for a de-escalation from all sides and we agree with that. But the attacks against our troops need to stop and that is why the president ordered the operation last night in self-defense of our personnel.”

Biden spoke alongside visiting Israeli President Reuven Rivlin, whose government remains firmly opposed to the 2015 international nuclear deal with Iran and skeptical of Biden’s efforts to rejoin it.

Rivlin presided over the creation of a new coalition government in Israel this month, but he will leave office July 7 after a seven-year term. Prime Minister Naftali Bennett has taken a less confrontational tone over the Iran deal than his predecessor, Benjamin Netanyahu.

Biden stressed the main area of agreement with Israel over Iran and said he intends to soon meet with Bennett at the White House.

“What I can say to you: Iran will never get a nuclear weapon on my watch,” Biden said.

Rivlin smiled as he said that the strong bond between Israel and the United States can withstand some strains.

“We, according to a real friendship, can from time to time discuss matters and even . . . agree not to agree about everything,” Rivlin said. “But we count on you.”

Six rounds of negotiations in Vienna have yet to reach agreement on a deal both the Biden administration and Iran’s leadership are eager to restore.

Iran is seeking the lifting of hundreds of U.S.-imposed sanctions that have throttled its economy. The Biden administration wants Iran to return to compliance with the terms of the nuclear deal and to hold talks aimed at curbing Tehran’s support for proxy forces in the Middle East as well as its development of ballistic missiles.

The victory this month in Iran of Ebrahim Raisi, a hard-line cleric who opposes negotiations with the United States, has added to the sense of urgency hovering over the talks. Raisi, who replaces President Hassan Rouhani, a political moderate, will assume office in August.