An outside panel chartered by the Pentagon has concluded that the rush to deploy a national antimissile system last year led to shortfalls in quality controls and engineering procedures that could have better assured the system would work, according to the panel's final report.

Bent on meeting President Bush's deadline to install the first elements of the system by the end of 2004, Pentagon officials put schedule ahead of performance, the report says. Among risky shortcuts that were taken, the panel says, were insufficient ground tests of key components, a lack of specifications and standards, and a tendency to postpone resolution of nettlesome issues.

"Manage quality first and then schedule," the panel advises.

The three panelists, all rocketry experts, offer no judgment on Bush's justification for hastily deploying the system: to counter a potential missile attack by North Korea. The U.S. intelligence community has reported that North Korea already can shoot a long-range missile at the United States, but some specialists have challenged this assessment, arguing the difficulty of developing such a missile and noting that North Korea has yet to flight-test one.

In any case, the panel makes clear that the U.S. decision to press ahead with the antimissile system in the face of production and testing delays has come at considerable cost in assurances of its reliability. Pentagon officials have blamed a recent string of system flight-test failures on minor technical glitches. But the panel argues that the setbacks reflected a larger preoccupation with deadlines.

As examples of how the tests were rushed, the panel notes that before an attempted flight in December, an interceptor missile was shipped to the launch site "with open issues" to be resolved in the field. Two days before another test in February, more than 20 problems had yet to be fixed -- an unusually high number of items to have pending so close to a flight test.

Such circumstances raised the risk of failure, the panel says. Indeed, both the December and February tests flopped, as did the preceding test, in late 2003.

Warning that more test failures probably would occur unless lower priority is given to meeting deadlines, the panel recommends that Pentagon leaders "reorient the program" to place greater emphasis on verifying reliability and make successful testing "the primary objective."

This "new phase" of the program, the panel adds, should "be event-driven rather than schedule-driven." And it should include more ground testing, more rigorous pretest certification procedures, more specifications and standards, and tougher measures for holding contractors accountable for performance, the panel says.

The panel's report reinforces concerns expressed by some Democratic lawmakers, scientists and other critics that the administration has moved too quickly to build an antimissile system whose effectiveness is still questionable and whose ultimate price tag -- in the tens of billions of dollars -- is excessive.

A spokesman for the Pentagon's Missile Defense Agency (MDA) said the panel's recommendations remain under review by Rear Adm. Kathleen Paige, who is heading the new post of director of "mission readiness," but probably will result in major procedural and scheduling changes.

Eight missile interceptors, designed to soar into space and knock down enemy warheads, are already at launch sites in Alaska and California, and more are due for installation in Alaska this year. But Defense Secretary Donald H. Rumsfeld has put off a decision to place the antimissile system on round-the-clock alert.

The panel's report, completed in March, has not been publicly released. Some of its findings were disclosed during congressional testimony in April by Air Force Lt. Gen. Henry A. "Trey" Obering III, the MDA's director. But the report itself is more critical than Obering indicated.

The full report remains classified. An unclassified, 37-page version prepared by the MDA was made available to The Washington Post by a government official who monitors the program.

Bush made construction of a national antimissile system a priority after taking office in 2001 and has invested as much as $10 billion a year in development of various missile defense technologies. His effort represents a scaled-down version of the expansive network envisioned by President Ronald Reagan two decades ago -- and dubbed "Star Wars" by critics. While Reagan imagined a shield against a massive Soviet attack, Bush favors a more limited system aimed at thwarting a small number of ballistic missiles that might be fired at the United States not by a major power such as Russia or China, but by a smaller adversary such as North Korea or Iran.

A series of successful flight tests in 2002 and 2003 led Pentagon officials to assert that the basic technological principle underlying the new system -- use of a missile to hit a missile -- could work, although critics have assailed the early tests as unrealistic and inconclusive. The tests started to go wrong in December 2003 when the system's "kill vehicle," a package of sensors and thrusters designed to ram into an enemy warhead, failed to separate from its booster rocket. Officials subsequently attributed the failure to a missing piece of foam insulation in a circuit board.

A two-year delay in system flight tests followed as Pentagon officials waited for development of an improved booster rocket. But two attempts to launch the new interceptor since late 2004 have been aborted at the last minute. Defense officials cited a flawed software code in December and a faulty silo retracting arm in February.

The test flops prompted Obering to request the outside review by the three experts -- William Graham, onetime head of NASA; Willie Nance, a retired two-star Army general who oversaw development of the missile defense system from 1998 to 2001; and William Ballhaus Jr., who heads the Aerospace Corp.

Their report contains no mention of any fundamental flaw in design of the system. But the panelists note the difficulty of building it, calling it "one of the most complex military systems that has ever been deployed," and likening its rapid development to the initial fielding of Minuteman nuclear missiles and submarine-launched Polaris missiles in the early 1960s.