Republican opponents of President Obama's request for authorization to strike Syria are increasingly pointing to the Syrian opposition's affiliation with al Qaeda forces as a reason not to pull the trigger.

To emphasize that an attack on Syrian dictator Bashar Assad would assist the terrorist group, one lawmaker wants the House vote on the Syria authorization to take place on 9/11.

"I believe the House vote on the resolution authorizing the use of military force in Syria should be held on Wednesday, September 11, the twelfth anniversary of the 9/11 attacks," Rep. John Culberson, R-Texas, said Thursday.

"This will give clarity to the debate, and by defeating the resolution, the House will honor the victims of 9/11 by refusing to support al Qaeda," Culbertson said.

House Speaker John Boehner, R-Ohio, plans to have the vote next week, but a date has not been set. Even if Boehner denies Culberson's request, the proximity to the anniversary of the September 11 terrorist attacks gives opponents a potentially powerful hook for one of their favorite talking points.

Sen. Rand Paul, R-Ky., noted the "irony" of the U.S. supporting Syrian opposition groups when the Senate debated providing military assistance to the rebels.

“You will be funding, today, the allies of al Qaeda," Paul said on May 21, 2013, during a Senate Foreign Relations Committee hearing.

Sen. Ted Cruz, R-Texas, made a similar point when he claimed that an attack on Syria would turn the U.S. military into "Al Qaeda’s air force.”

Not all Republicans agree. "I believe that is a cheap line by some people to garner headlines, and not a serious discussion about what is going on,” Rep. Adam Kinzinger, R-Ill., said during a House Foreign Affairs Committee hearing Wednesday after quoting Cruz's comment without mentioning the Texas senator by name.

Secretary of State John Kerry tried to put fears of helping al Qaeda to rest when he told a Senate panel that the opposition "has increasingly become more defined by its moderation, more defined by the breadth of its membership, and more defined by its adherence to some, you know, democratic process and to an all-inclusive, minority-protecting constitution."

The concern persists, though.

"Every time I get briefed on this it gets worse and worse because the majority now of these rebel forces, and I say majority now, are radical Islamists pouring in from all over the world to come to Syria for the fight, and my concern is any strike against this regime, as bad as it is, will empower these radical Islamists, these extremists," Rep. Michael McCaul, R-Texas, said during a House Foreign Affairs Committee hearing.