President Barack Obama declared a war against the ISIL group back in September with administration officials saying the US president had the power to take action unilaterally based on the Authorization for Use of Military Force passed by Congress in the aftermath of the Sept. 11 attacks.
Lawmakers in both parties, however, believe the Obama administration does not have the authority to wage a new war in the Middle East that has not been properly authorized by Congress.
Republican Senator Rand Paul of Kentucky, a likely presidential contender, attempted to force a vote on a declaration of war Thursday. Paul offered his legislation as a last-minute amendment to an obscure clean water bill.
Republicans on the Senate Foreign Relations Committee raised objections and Sen. Paul eventually withdrew his proposal under the promise that he would get a separate debate on the issue.
House Speaker John Boehner said Obama should submit an authorization in the new Congress.
"I've got grave concerns that ... the plan he's put in place is not going to accomplish the goal of defeating and destroying ISIL," said Boehner.
Democrats on the Senate Foreign Relations Committee also launched a last-ditch effort on Thursday for a legal justification for the military campaign against ISIL. Outgoing Democratic chairman, Sen. Bob Menendez, said members had reached an agreement to hold hearings with an eye towards voting on an authorization next week.
Senators will discuss the issue with administration officials during a public hearing on Monday. Menendez said Secretary of State John Kerry or another top official from the Obama administration would testify at a hearing.
Republicans, however, said even if the Democrats accomplish the authorization, the House and the Senate would ignore it when they gain control of Congress. Democrats will hand full control of Congress over to Republicans next month.
President Obama ordered airstrikes against ISIL targets in Syria in September. The air campaign is an extension of air raids in Iraq conducted since August.
The ISIL group made swift advances in much of northern and western Iraq over the summer after capturing large swaths of northern Syria. The US-led campaign has been widely criticized for failing to effectively limit the advance of the militants.