ABMs or BMD will give India an elate sense of security (as one of our nuclear strategists puts it) but here are some important pointers that should not be sidelined. (This is just a general information ... not directed towards India or any other country for that matter).
i. Too expensive to protect a city let alone a country (especially the size of USA, Russia, China, Brazil, India etc ...)
ii. Can only target BM in its terminal stage.
iii. Its success rate has only increased by 5% in past 6 years (from 65% to 70% - there is still 30% to 25% chance it will miss the target coming down at very high speed).
iv. Not effective against Cruise Missiles.
v. Not much effective against MIRVs.
vi. Not effective against multiple missiles (this is why Iran held exercise of multiple missile launch).
vii. Smart Ballistic Missiles are being considered as counter of ABMs and are considered much cheaper-opposite method. Russians have hinted towards working on such system.
India seems to be following the patterns of Bush Administration's "Nuclear Posture Review" especially with regards to ABMs. But the question is; is it feasible for India to continue making model out of NPR-2001 when most of the American nuclear experts are calling on democrats reverse it, especially the BMD section?