I don't think "nothing" is an acceptable approach at this point.
Amb. Marc Ginsberg had these suggestions, and they also seem like worthy considerations to me:
"If the Administration continues on its present, relatively passive course and shirks America's duty and responsibility to confront the Russian Syrian arms transfers with tougher resolve, it won't be merely "leading from behind;" it will be turning its back on the growing humanitarian catastrophe in Syria.
So what can the U.S. realistically do without landing marines on the beaches of Syria:
1. Call Russia's bluff. Force a UN Security Council resolution vote demanding an arms embargo on Syria and dare the Russians veto it.
2. Expel Russia from the G-8 until it ceases arms transfer to Syria. Freeze Russia out of some other international gatherings and forums for good measure.
3. Straightjacket the Central Bank of Syria by completely cutting off its access to U.S. and European banking facilities.
4. Develop support for an international indictment in the International Criminal Court against the Assad regime's leadership for crimes against humanity.
5. Encourage Arab League efforts to organize a military supply airlift through southern Turkey to provide additional support to the Free Syrian Army.
6. Officially delegitimize the Assad regime by recognizing the Syrian National Council as the new, legitimate government of Syria, and galvanize European Union and Arab League nations to follow suit.
7. Provide additional financial and diplomatic support to the Syrian National Council to form a Syrian government in exile and have its leadership publicly embraced in western and Arab capitals.
8. Work with Turkey to declare and enforce a humanitarian zone in northern Syria to provide shelter for Syrians fleeing the fighting."
http://www.huffingtonpost.com/amb-marc-g...64530.html