Russia has 150,000 soldiers outside the border, NATO is holding a security meeting today to decide on the course of action, US already stated they would get involved if Putin did not pull back.
Russia has broken international law, they are an obvious threat. The allied forces see this and will not just let it slide.
Update: Unidentified military ship has just been spotted off the coast of Sevastopol, thought to be US but most likely more Russian's.