put the situation into the hands of the U.N. - difficult with Russia and China's veto, but the alternative doesn't bear thinking about.

For "difficult" read "impossible". After what happened with the UN go ahead in Libya, in which a very carefully limited approval got hijacked, and turned into a full-blooded air campaign to force regime change, Russia is not going to be tricked in that way again. The alternative may not bear thinking about, but it's going to have to be a case of grin and bear to think about it anyway.