The House of Representatives rejected an amendment to a defense bill on Thursday that would have forced lawmakers to vote on a formal authorization for the use of military force against Islamic State.
The House voted 231 to 196 to defeat the amendment sponsored by Representative Adam Schiff. Republicans, who control a majority of seats in the House, largely voted against the amendment and Schiff's fellow Democrats generally backed it.
The vote took place a day after President Barack Obama ordered the deployment of 450 additional U.S. troops to Iraq to advise and assist Iraqi forces seeking to retake territory lost to Islamic State.
The amendment would have required Congress to debate and vote on a new authorization by March 31, 2016, prohibiting funds in next year's defense appropriations bill to be used for the campaign of air strikes against Islamic State until Congress passed an authorization.
Obama asked Congress in February to approve an authorization for the use of military force (AUMF) against the militant group after agitation from lawmakers worried that the military campaign he began in August overstepped his constitutional authority.
But Congress has failed to take up the issue. Republicans, who criticize Obama's foreign policy as too passive, say they want stronger measures against the militant fighters than those proposed by Obama.
And many of Obama's fellow Democrats are wary that approving an AUMF would lead to another large, enduring deployment of U.S. troops in the Middle East.
Schiff is one of a handful of lawmakers who have been pushing for Congress to pass an AUMF.
"If we're going to ask our service members to risk their lives, we ought to have the courage ourselves to take a vote on this war," he said.