Issa said such a focus would seem to legitimize attacks by a government on its own people using conventional weapons.

"Tens of thousands have been killed by the Assad regime in this brutal conflict -- relatively few by chemical weapons. A military response that places an arbitrary focus on such weapons will do little to protect civilians and sends a deeply misguided signal that totalitarian regimes should only use conventional weapons to carry out mass murder," he said in a statement issued Monday.

Issa said he remains undecided on approving military action in the country, and to earn his support, "President Obama must present a clear plan focused on effective humanitarian intervention or our national security interests."

President Obama said Saturday that while he believes a military attack on Syria is necessary, he'll seek congressional approval before moving forward.

Secretary of State John KerryJohn Forbes KerryTrump's rejection of the Arms Trade Treaty Is based on reality Chimamanda Ngozi Adichie becomes first African to deliver Yale graduation speech Dem Sen. Markey faces potential primary challenge in Massachusetts MORE on Friday made the case for U.S. military engagement to respond to the Syrian government's alleged use of chemical weapons, which he called a "crime against humanity."

He revealed on Sunday that samples collected by first responders after the Aug. 21 attack by the Syrian government tested positive for Sarin, the latest evidence of a chemical weapons attack.

But Congress, and the American public, remains largely divided on whether military engagement in Syria is necessary.

The White House has launched an intensive outreach effort to move congressional opinion to support an attack, with a vote on a resolution to approve the use of military force expected the week of Sept. 9.