In a war of attrition between Muslim Islamist militant factions, it is wise to back neither side. So long as al Qaeda is engaged with fighting Bashar al-Assad, they are not available to be opening a front elsewhere.
But we now have John Kerry (who once served in Viet Nam, you know) as Secretary of State, and he has definitely broken with Bashar, contrary to his earlier declarations of support only a few months ago. One could only wish that Kerry would undertake a similar break with al Qaeda.
One is reminded of the Molotov-Von Ribbenthrop treaty between Nazi Germany and the Soviet Union.