House lawmakers rejected a measure giving President Obama the authority to continue U.S. military action against Libya.
The 295-123 vote represents a rebuke of the president for what congressmen see as his flagrant disregard for the Constitution.
"The president has ignored the Constitution and the War Powers Resolution, but he cannot ignore a lack of funding," said Rep. Tom Rooney, R-Fla., sponsor of the bill.
"Only Congress has the power to declare war and the power of the purse, and my bill exercises both of those powers by blocking funds for the war in Libya unless the president receives congressional authorization," Rooney added.
Meanwhile, Secretary of State Hillary Clinton appealed privately to House Democrats Thursday, saying now is not the time to cut off funds for the Libya mission.
"The secretary expressed her deep concern that you're probably not on the right track when Gadhafi supports your efforts," Rep. Tim Walz, D-Minn., said.
California Rep. Howard Berman, the top Democrat on the House Foreign Affairs Committee, agreed, saying such a vote "ensures the failure of the whole mission."
But House Speaker John Boehner, R-Ohio, made it clear that the vote was not intended to undermine NATO.
"I don't want to do anything that would undermine NATO or to send a signal to our allies around the world that we are not going to be engaged," Boehner told reporters.
"This is primarily a fight between the Congress and the president over his unwillingness to consult with us before making this decision," he said.