Long range tracking systems are good enough now that Russia, China or other 1st world nation would have a good idea what the target is shortly after launch, and nobody is going to start WWIII over a single launch.
I'm far more worried about the cost of such a system. A global ballistic or cruise missile would probably cost millions, if not tens of millions, per unit. We could easily end up with a system that we can't afford to actually use.
Jay