Senate Republicans on Wednesday blocked an effort by Democrats to stop continued U.S. military strikes on boats alleged to be carrying drugs off the coast of Venezuela.

In a 48-51 vote, the Senate rejected a resolution led by Democratic Sens. Adam Schiff of California and Tim Kaine of Virginia. The measure, brought under the War Powers Act, would have prohibited the U.S. military from engaging in hostilities with “any non-state organization engaged in the promotion, trafficking, and distribution of illegal drugs and other related activities” without explicit congressional authorization, CBS News reported.

“There has been no authorization to use force by Congress in this way,” Schiff said before the vote. “The strikes risk escalating into a full-blown conflict with Venezuela. I feel it is plainly unconstitutional.”

The Trump administration has confirmed conducting four strikes on alleged drug-trafficking boats since Sept. 2, killing at least 21 people. Officials say the strikes targeted vessels linked to Venezuela’s Tren de Aragua, Mexico’s Sinaloa Cartel, and El Salvador’s MS-13, which the administration designated as foreign terrorist organizations.

In a report to Congress after the second strike in mid-September, the White House said the U.S. is engaged in a “non-international armed conflict” with drug cartels, which it described as posing an “armed attack” against American citizens. The administration argues the cartels’ role in smuggling deadly narcotics constitutes a national security threat equivalent to terrorism.

Secretary of State Marco Rubio, who met with Senate Republicans at the Capitol on Wednesday, defended the strikes and said the president has the authority to act without congressional approval.

“These are targeted strikes against imminent threats against the United States,” Rubio said.

Democrats and some Republicans have questioned the legal basis of that claim. Kaine said the administration has refused to provide lawmakers with intelligence supporting the strikes, the rationale for attacking the boats instead of intercepting them, or the legal justification for the ongoing campaign.

“The White House does not maintain there’s any congressional authorization,” Kaine said. “These military actions should stop unless authorized by Congress — not permanently, but until Congress acts.”

Under the War Powers Resolution of 1973, the president must consult Congress before introducing U.S. forces into hostilities unless there has been a declaration of war or other authorization. Without congressional approval, the president must withdraw forces within 90 days. The law was passed after the Vietnam War to limit unilateral presidential war powers.

Republican Sen. Rand Paul of Kentucky has been one of the most vocal GOP critics of the strikes. After the first strike, Paul condemned Vice President JD Vance, who had said that “killing cartel members who poison our fellow citizens is the highest and best use of our military.”

“What a despicable and thoughtless sentiment it is to glorify killing someone without a trial,” Paul wrote at the time.

Paul reiterated his objections in a Senate floor speech Wednesday, saying the administration has provided no evidence that the targeted boats were actually carrying drugs.

“If anyone gave a you-know-what about justice, perhaps those in charge of deciding whom to kill might let us know their names, present proof of their guilt, show evidence of their crimes,” Paul said. “Is it too much to ask to know the names of those we kill before we kill them?”

Other Republicans defended the strikes. Sen. Mike Crapo of Idaho said the president’s actions were “fully compliant and fully justified.”

The debate echoes previous clashes over war powers. Earlier this year, Congress rejected a similar resolution from Kaine seeking to restrict the president’s ability to use force against Iran after U.S. airstrikes targeted Iranian nuclear facilities.

Schiff warned that allowing presidents to unilaterally order military action sets a dangerous precedent.

“We’re blowing up ships thousands of miles from our shore,” Schiff said. “What is to stop another nation from doing the same thing and calling it self-defense? That’s not a precedent we should want to see repeated.”