Do you see the little problem here? You are notoriously trying to hit a bullet with a bullet, and relying on guidance to fine tune the intercept trajectory. From whence comes that guidance?
The B in ICBM is "Ballistic:" the warheads fly like a rock. They get their direction in the boost phase (which for fast solid state boosters is 90 seconds). That part of the trajectory shows up like a searchlight, but it is kind of hard to triangulate from above and is invisible around the curvature of the earth if you're too far away. From then until near the end of its journey it is just a warmish object sailing along like any harmless low speed meteor.
Aha, you say: Just locate its orbit, and those of its comrades, with radar and send the adjustments to our defense missiles to home in on them. Problem is that countermeasures are pretty easy: lots of lightweight decoys to confuse you, or just let one of the warheads go off in space and mess up radar for several minutes. (Or just time your launch for a solar flare.)
Wikipedia has a little history of this sort of thing. Boost phase interception might work against North Korea, but not China.