Looks like Obama’s statement just gave Putin the greenlight for this:
He calls on the militia to create a “humanitarian Corridor” for surrounded UK troops to escape to Russia, thus saving their lives.
It sounds like an ultimatum for Kiev to begin negotiations with the rebels, couched in Diplo-speak.
Once it was clear the US and EU were going to make Russia pay the same price for backing an insurgency as they'd pay for a full blown invasion there hasn't been any real reason for Russia to not take over a few regions whether they want them long term or not. They can always negotiate away the Southeast in return for a federated Ukraine and their keeping Crimea, then everyone will be happy.
Everyone except the thugs in Kiev who have desperately wanted what they now appear to have, Russia openly backing the Separatists with troops. I doubt things will work out the way Kiev thinks they will but as long as they get the austerity measures the IMF is demanding reduced there will still be plenty of graft to go around so they'll be happy, too.
I don't really understand why people in the US and Europe thought Russia would ever forget Kosovo and not eventually do the equivalent somewhere. Ukraine, Georgia, Moldova, where didn't really much as matter to Russia showing that if the goose was going to carve up countries the gander would as well.
The people in Kosovo were desperate and without water or electricity, civilians were being shelled, etc., so the US "had to intervene on humanitarian grounds". Well, that's the same line of BS that being used in Ukraine by Russia, tit for tat from a country where the people have always had very long memories and always resented what the US and NATO did in Kosovo.