He would stay out of it.
Common sense alone dictates that you do not willingly and actively join a fight that is a 'no win' situation.
And loki8481 point about this being a potential slippery slope is valid.
Does anyone not realize that by Obama announcing aid to the rebels the other side (Iran, Russia etc.) will just step up their support for the Assad regime? What are we really trying to accomplishing here? What is our objective both short-term and long-term? Has this been thought out at all by this administration? I see no evidence it has.
Fern
Of course Obama/Pentagon et al know exactly what they are doing.
They know very well they are turning Syria into Afghanistan II.
Now you have to ask yourself why they are doing it. The US is taking a sledge hammer to every Muslim state they can and shatter them along tribal lines and push them into eternal conflict. Flaming every tribal conflict in Muslim nations, arming opponents to they can start grueling decades long wars, all of that is done on purpose with a strategic aim, the good old 'Divide and Conquer'.
One reason is that if Syria breaks Hezbollah weakens. Hezbollah has twice defeated Israel and repelled Israeli invasions of Lebanon.
With the new bunker buster bombs provided by the US and Syria in turmoil invasion number 3 is set up perfectly. This time a weakened Hezbollah would find it harder to resist a stronger Israel. Israel wants revenge and it wants the large aquifers in Lebanon and more land for Greater Israel.
Even if there is no new invasion it has been the US and Western ME strategy for decades, a century in fact, to not allow any Muslim nation to grow strong and independent and form alliances with equally strong neighbors. For that end the US has propped up any number of odious dictators and medieval kingdoms.
See the Sykes-Picot agreement for how the game is played.
http://en.wikipedia.org/wiki/Sykes–Picot_Agreement