WASHINGTON (AP) — A bipartisan group of lawmakers is raising concerns over a series of recent U.S. military strikes against Yemen Houthi rebels, urging the Biden administration to get congressional authorization before taking further military action in the Middle East.

In a letter to President Joe Biden on Friday, a coalition of nearly 30 House members expressed their strong opposition to what they described as “unauthorized” American strikes that have further escalated the biggest confrontation at sea the U.S. Navy has seen in the Middle East in a decade.

“As representatives of the American people, Congress must engage in robust debate before American servicemembers are put in harm’s way and before more U.S. taxpayer dollars are spent on yet another war in the Middle East,” the letter, led by Rep. Ro Khanna, D-Calif., and Rep. Warren Davidson, R-Ohio, stated. “No President, regardless of political party, has the constitutional authority to bypass Congress on matters of war.”

The lawmakers, who hail from the far-right and far-left of their respective parties, represent a small but growing faction in Congress that is skeptical of the nation’s increasing involvement in the Middle East in recent months.

The White House, for their part, has defended the multiple rounds of airstrikes it has taken in partnership with the United Kingdom since early January in response to what has been a persistent campaign of Houthi drone and missile attacks on commercial ships since the start of the Israel-Hamas war in October.

Since the beginning of the year, Biden has written several times to Congress stating that the strikes have complied with the 1973 War Powers Act. That law, passed during the Vietnam War, serves as a constitutional check on presidential power to declare war without congressional consent. It requires presidents to notify Congress within 48 hours of military action and limits the use of military forces to no more than 60 days unless Congress authorizes force or declares war.

But lawmakers, including a bipartisan group of senators, have said that decades-old statute does not give the president the “blanket authority” to take military action simply by notifying Congress within 48 hours.

The letter from Khanna and Davidson asserts that the notification only stands if the commander-in-chief “must act due to an attack or imminent attack against the United States.” They said the escalating tensions in the Middle East do not rise to that level.

“We ask that your Administration outlines for us the legal authority used to conduct these strikes, and we urge your Administration to seek authorization from Congress before conducting any more unauthorized strikes in Yemen,” the lawmakers wrote.

Biden has stated that the U.S. would continue the strikes against the Houthis, even though so far they have failed to deter the group from further harassing commercial and military vessels in the region.

When asked by reporters last week if he believes the strikes are working, Biden said, “When you say ‘working,’ are they stopping the Houthis? No.”

He added, “Are they going to continue? Yes.”