Among them is to let allies in the Persian Gulf equip rebels with more modern weapons. Obama's Administration opposed it being afraid that the ISIS or al-Qaeda may get it.
Another, the most tough, is airstrikes on the Syrian Air Force bases, not far from combat acts between Assad's troops and rebels in the north of the country. This option was also turned down because of possible casualty among the Russian military.
Solutions which have been discussed also comprise deployment of a bigger contingent of the US Special Operations Forces to train and consult the Kurdish and Syrian rebel groups, as well as deployment of additional US Air Forces and the Navy - including those of the coalition - in the eastern part of the Mediterranean Sea.
Speed at which the Syrian military attacks Aleppo and difficulties with diplomatic settlement of the conflict have taken Obama's Administration aback. They believe in case Assad's troops take back Aleppo, it'll be a devastating blow for rebels. As Pravda.Ru reported, on 28 September the US State Secretary John Kerry claimed that the US was going to stop cooperation with Russia on Syria.
The West, together with Ukraine, quickly forms a strike corps in order to enter Crimea or cut off the Donbass from Russia