In short: They are stalling for time.
But what they need the time for? To occupy as much land as possible, but that is only the surface level of the war. This war is not a simple war for land, but a war for attrition.
The US is reached 37 billion, and Russia was one of their major target for the soft-occupation driven resource extraction, like they did with Latin-America. Simply, none else left in the world to rob.
China, India became too strong, and the US is heavily exposed to them in terms of IT jobs and manufacturing. EU is a wasteland, they don't have any money left.
Rest of the world? Not going to work, as they are either struggling areas, like Africa. US can't build on arab allies like the Saudis, as they can "spare" 500 billion in every 2-3 year to "invest" into the US, but the debt clock is ticking faster.
This is a war of attrition against the US, and a successful one. US announced in Alaska they want to leave it finally - and they will -, but the Russians will squeeze every last drop of it.