The flight test, which was already delayed several times, had most recently been slated to occur at the end of September. But Lt. Gen. Henry A. "Trey" Obering III, director of the Pentagon's Missile Defense Agency (MDA), told The Washington Post that he decided to delay it until the end of November because of technical considerations.

   Obering said the setback will not affect plans to begin operating the system in the next month or two. President George W. Bush has made it a key goal of his administration to deploy a preliminary missile defense system before the November election.

   But the delay means the system would be deployed without a flight test in nearly two years. After several successful intercepts since Bush's election, the system failed to intercept a mock enemy missile in a test in December 2002.

   After that failure, MDA officials ordered a halt to more intercept tests until a newly designed booster could be completed. Obering said he decided to delay the test again after learning last week of a number of modifications to the test interceptor that were not checked out fully in ground tests.

   Another factor contributing to the delay was the inability so far to find the root cause of a software glitch in the flight computer of the interceptor's booster rocket, the Air Force general said. That glitch led to an earlier flight test delay from mid-August to late September.

   Democratic lawmakers and other critics of the system accused the Bush administration of playing politics with the test schedule, seeking to avoid the risk of an embarrassing flop during the presidential campaign.

   "This has been a program so fraught with political calculation, rather than strategic and scientific thought, that I would assumethere's some political aspect to the delay," Senator Jack Reed, Democrat from Rhode Island and a member of the Armed Services Committee, told the Post.

   The postponement also comes against the backdrop of a wide disparity in estimates about the system's likely effectiveness that has emerged among key Pentagon officials.

   The Pentagon's chief weapons evaluator has calculated that the system may be capable of hitting its targets only about 20 percent of the time. But the MDA, which is responsible for developing the system, offers estimates of greater than 80 percent, the Post said, citing officials familiar with the classified figures.  Enditem