The problem is that the same US ABM missile sites in Poland and the Czech Republic could be used to launch short-range missiles designed to cut the Russian command and control network.  This has been US strategy for DECADES, but there has been no practical way to implement it.  Close-basing near the Russian border is thought to provide the practical way to make the first-strike strategy operational.  

This leaves the Russians only with their automatic dead-hand system, but obviously they do not want to be relying solely on that.  

The Russians will have to take SOME practical counter-measure before the US has established those bases.  I do not know what it will be, and it does not sound like the Russians do either.  So the warning to the Poles and Czechs that they can expect to fry at the first sign of trouble, is meant to warn them off of this thing and slow it down.  

The Fates are kind.