WASHINGTON - In an apparent setback on the Pentagon's drive to develop a national missile defense, a prototype missile interceptor streaked into space Tuesday night in search of a mock warhead launched from an Air Force base in California but failed to hit the target, a Pentagon official announced.
''An intercept was not achieved for reasons unknown at this time,'' spokesman Air Force Lt. Col. Rick Lehner said.
The mock warhead was meant to simulate a nuclear attack on the United States, and a successful intercept would have provided a dramatic boost to the Pentagon's effort to show missile defense can work.
The interceptor rocket was launched from a U.S. Army missile range on Kwajalein Atoll in the Marshall Islands, about 20 minutes after the target missile lifted off from Vandenberg Air Force Base at 6:19 p.m. and headed over the Pacific Ocean.
The light from the missile flashed in the sky over much of Northern Nevada on Tuesday evening.
A Fallon Naval Air Station watch commander said his office had received several calls from a wide geographic area reporting "bright lights." He said flashes were visible in Carson City, Hawthorne and Fernley.
A Carson City dispatcher said that an "unofficial source" called earlier in the day, reporting that some missile testing over the Pacific Ocean might be visible in the Tahoe area. She also reported several calls about the lights.
A National Weather Service forecaster said that it is unlikely that flashes in the sky could be related to any weather phenomena.
Lehner said Pentagon officials would conduct an extensive review of the test data to determine why the interceptor missed the target. He said the first preliminary report would not be available for at least 48 hours.
The interceptor launch went off as planned, Lehner said. ''What happened after it got into space we do not know,'' he said.
Pentagon officials had asserted before the test that even if the interceptor failed to hit its target, there were other important goals for the test, including the first test of a computerized battle management system that is designed to communicate with the interceptor as it soars into space.
Lehner said there was no immediate word on whether these other aspects of the test worked as planned.
In remarks to reporters several hours before the test, Pentagon spokesman Kenneth Bacon said that if the interceptor, called a ''kill vehicle,'' succeeded in hitting the target warhead - and if all of the radar, communications and other technical aspects of the test worked correctly - then the Pentagon would have met its self-defined minimum standard for recommending that the system is feasible to deploy.
An initial test last October resulted in a successful intercept.
''I think we just have to wait until all the results are in and see how they mesh together before we can say it's a successful integrated systems test,'' Bacon told reporters before the scheduled start of the test.
More than a dozen protesters held a vigil outside Vandenberg Air Force Base on Tuesday to protest the test. ''We were all holding up signs protesting this wrongheaded thing our government is doing,'' said Bud Boothe, 74, a member of the Global Network Against Weapons and Nuclear Power in Space.
Nuclear powers Russia and China are the most vocal opponents of a proposed U.S. national missile defense, but it is North Korea - economically destitute, politically isolated and militarily hostile - that Clinton administration officials say poses the most immediate missile threat.
Thus the initial version of a national missile defense, as envisioned by Pentagon planners, would be designed mainly to counter a small-scale attack from North Korea. More robust defenses might be added later to shield American territory from missile attacks by other so-called rogue nations, like Iraq or Iran.
President Clinton may decide as early as this summer whether to go ahead with a national missile defense, which the Pentagon estimates will cost at least $12.7 billion over the next five years. It could be ready for use by 2005, although many officials involved in the program believe that may be too ambitious.
Russia is concerned that a U.S. missile defense system would undermine the deterrent value of its nuclear missile arsenal, as is China.
John Hamre, the deputy U.S. defense secretary, said Tuesday that Russia and China need not worry about the U.S. system, which would be designed to counter limited missile attacks from ''rogue'' countries like North Korea.
In an interview in his Pentagon office, Hamre said North Korea is a legitimate source of worry about a surprise missile attack, since it has taken the apparently irrational course of investing heavily in developing a long-range missile capability even though no one is threatening it and even while many of its people are starving.
''There is no rational reason why North Korea, with the economic straits that they are in, would choose such a provocative thing to do,'' Hamre said. ''This is a country that doesn't care about the opinion of the international community,'' and therefore must be judged capable of attacking the United States unprovoked.