PRESIDENT George Bush outlined his vision of a national missile-defence programme last week. Many critics say the scheme will be ineffective and staggeringly expensive.

Bush revealed sketchy details of his concept of a "layered" defence system, which would force enemy missiles to evade a series of ground, sea and air defences. The scheme is far more modest than Ronald Reagan's space-based Strategic Defense Initiative (SDI) or "Star Wars" proposal of the early 1980s. SDI sought to block a full-scale attack by the now defunct Soviet Union, while Bush's proposed system seeks only to stop a few missiles from a rogue state.

One layer of the proposed system would be the ground-based National Missile Defense System originally developed under the Clinton administration. After a failed test last year, Clinton passed the job of deciding whether to deploy the system to his successor, pending further tests that are still to be carried ...