Defence against what?
There is no particular reason why the United States, or any other nation, should cancel an important strategic programme just because China opposes it. Neither should China shape its own defence plans solely according to what other governments say. Each country must choose thoughtful policies that meet its own national needs in the long term.
That said, there are plenty of reasons for Washington to heed the advice of 45 American Sinologists, including a former US ambassador to Beijing, who want to delay the pending National Missile Defence system, or NMD. In a letter to President Bill Clinton last week, they said a 'precipitous decision' to go forward would increase US-China tensions needlessly and lead Beijing to accelerate its own long-range missile programme.
In some ways, the NMD is a US$60 billion (HK$467 billion) plan seeking a rationale. It was originally conceived to defend America from the small missile forces of so-called 'rogue states', notably North Korea. Mr Clinton has said he will decide this autumn whether to approve step one, building a high-powered radar station on a remote Alaskan island. By 2005, the plan calls for siting 20 missile interceptors in Alaska, with more than 200 others to follow in various other states, including Greenland and Britain.
But things change. The US has officially dropped the term 'rogue states' for the less-menacing 'countries of concern'. North Korea has put its missile plans on hold and seems en route to establishing normal relations with the outside world. Those Alaskan components might well defend against an enemy that no longer exists.
Beyond that, there are substantial doubts about whether the costly system will work - early tests have been discouraging. For one thing, no one knows if the missile interceptors will ever be able to tell real warheads from decoys in the 100 seconds they have to decide.
China contends it is the true NMD target, no matter how often Washington denies it. Some harsh anti-China words in the current US political campaign add to this belief. Given the doubts about the system's purpose and effectiveness, Mr Clinton's best move at this time would be to hand over any decisions to his successor.