Obama has already lost this battle. Crimea is with the Russia permanently now. It is replay of Georgia events six years back. US instigated trouble in Georgia and then made empty threats. Russians came and seized the Russian speaking lands and thumbed at the Americans. The same is happening in Ukraine.
Just one question, what business is Ukraine to Americans. It is the latter who instigated the trouble after a democratically elected government rejected the EU trade deal. A coup was organized by the Americans. It went out of control and the Americans blamed the Russians for murder. In fact a democratically elected government has been overthrown. It should be a concern for Americans. But Nay!, they like to blame the Russians.
If at all anybody should be out of Ukraine, it should be American and the Coup leaders. The Cremea referendum cannot be reversed. If the illegal government in KIEV can exist then illegal referendum in Cremea can also proceed.
Second question Mr. Obama, when did the sanction work in last fifty years. Did they work for 25 years in South Africa. Did they work in China, Iran or Libya or Serbia? You also virtually sanctioned Narendar Modi, the would be Indian Prime MinIster candidate. It is you who began to loose ground with sanctions and began talking to them.