Originally Published: 28 JUN 21 14:20 ET

By Allie Malloy, CNN

(CNN) -- President Joe Biden viewed precision airstrikes against Iran-backed militia groups on the Iraq-Syria border region as "necessary, appropriate and a deliberate action," press secretary Jen Psaki said Monday, defending the administration's legal justification for the strikes under Article II of the US Constitution.

On Sunday evening, Biden directed the strikes against facilities that were utilized by Iran-backed militias engaged in unmanned aerial vehicle (UAV) attacks against US personnel and facilities in Iraq, including operational and weapons storage facilities in Syria and Iraq, according to the Department of Defense.

The airstrikes come as the Biden administration is pursuing delicate negotiations with Tehran over a new nuclear deal. Psaki attempted to separate the issue, telling reporters: "We don't see that on the same track."

"We continue to believe, and have never held back from noting, that Iran is a bad actor in the region. At the same time we're moving forward, and seeking the opportunity to move forward on negotiations to prevent Iran from acquiring a nuclear weapon is in our national interests and that's how we will evaluate," Psaki said.

Asked whether the White House expects retaliation, Psaki said there will be "serious consequences" if Iranian leaders continue to arm and fund militia groups in the region.

"Our objective is to deescalate, but the President is going to reserve the option of responding when there is a threat against US interests," Psaki said.

She also told reporters that the White House is "confident" in the legal justification for the Sunday airstrikes through Article II.

The airstrikes were not the first ordered by this administration.

The US military's first known action under Biden came in February when it struck a site in Syria used by two Iranian-backed militia groups in response to rocket attacks on American forces in the region.

Those strikes generated concern among lawmakers, who said Biden had not asked for the necessary congressional authorization. The White House had also said the strikes were backed by Article II of the Constitution, as well as the United Nations charter.