Donald Rumsfeld, President-elect Bush's nominee for secretary of defense, is a leading proponent not only of national missile defenses, but also of U.S. efforts to take control of outer space by developing technology to attack and defend satellites in orbit. Together, these initiatives could bring a dramatic militarization of space over the next two decades, a prospect that some defense experts have long urged and others have passionately condemned.

The Pentagon is using national missile defense "as a wedge to accelerate our activities in space," charged Bruce Blair, head of the nonprofit Center for Defense Information. "It is inevitable," countered Richard Haass, a National Security Council staff member in the first Bush administration and now head of national security programs at the Brookings Institution. The combination of missile defenses and America's growing dependency on satellites "means space is no longer a sanctuary and is too central that we won't be challenged" by other countries developing anti-satellite weapons, Haass said.

The system that the Clinton administration was developing to protect the 50 states from ballistic missile attack would have been strictly land-based, with interceptor missiles launched from Alaska. It was to include some satellites for tracking enemy missiles, but no weapons based in space.

President-elect Bush, on the other hand, has said his administration will strive for a far more ambitious shield, possibly using space-based weaponry. Such weapons do not yet exist, but the United States has been working for years on powerful lasers that might someday be mounted on aircraft or satellites.

Rumsfeld chaired a commission that helped build political support for national missile defense by issuing a 1998 report warning that Iran and North Korea were closer than previously believed to having missiles that could reach the United States. Now, another congressionally mandated commission headed by Rumsfeld is finishing a report on threats to U.S. satellites, which are increasingly vital to military and civilian communications.

The report, expected in mid-January, will endorse "U.S. control of space, including defending our own satellites and engaging those of any enemy," according to a colleague of Rumsfeld. In a press conference announcing his nomination Thursday, Rumsfeld himself listed "defense of our space assets" as one of his top priorities.

John Pike, director of GlobalSecurity.org, a defense research organization, said some members of Congress pushed for the latest commission because they think the United States should be working harder to develop "anti-satellite weapons, lasers and other space weapons" and should consider establishing "a separate space force, much as we have a separate air force." In Pike's opinion, however, putting weapons in space would be "a singularly misguided track when we are the only nation with satellites worth shooting at."

Other countries -- particularly Russia and China, but also many U.S. allies -- oppose the U.S. missile defense effort and warn that it could set off an international arms race in space. If the United States builds a missile shield, "space will become a new weapons base and battlefield," Sha Zukang, head of the Chinese Foreign Ministry's disarmament department, said in June. "Since other big powers will not sit and look on unconcerned, this will inevitably mean the extension of the arms race into space."

The Outer Space Treaty, signed in 1967 by the United States and other major powers, prohibits placing nuclear weapons in orbit. The 1972 Anti-Ballistic Missile Treaty, which Bush wants to change or discard, outlaws space-based lasers to attack strategic intercontinental missiles, and a side agreement signed in 1997 in Helsinki carries that concept over to theater missiles. But no treaty bans anti-satellite weapons, which both the United States and Russia have been researching and testing for more than 20 years. The original impetus for developing these so-called ASATs was the prospect of space-based missile defense systems.

When President Reagan's Strategic Defense Initiative, or "Star Wars," plan was dropped by the first Bush administration, the race to develop ASATs receded back to research. Last August, the Army used a ground-based chemical laser to hit an aging U.S. military satellite in an apparent ASAT test that officials claimed had not been cleared in advance by the White House or State Department. When the test was publicized, the Pentagon said its purpose was to develop defenses for U.S. satellites. Russian diplomats, however, complained that the United States was preparing for war in space.

The fiscal 2001 Defense Department budget contains funds for numerous Army and Air Force ASAT programs, including $20 million for the Army's ground-based kinetic energy anti-satellite technology program, which began more than 20 years ago. An additional $5 million is marked "for the development of space control technologies that emphasize reversible or temporary effects." Some $30 million is allocated to prepare Kirtland Air Force Base in New Mexico as the central management point for the Pentagon's directed-energy laser programs.

The Air Force's Satellite Assessment Center, which studies satellites and their vulnerabilities, already is located at Kirtland. The budget also contains $73.2 million for a space-based laser program and $37.5 million for high-energy laser tests similar to the one last August. A classified $3 million research program called Big Crow could lead to devices that could "impede" enemy satellite operations, according to a congressional source.

Some experts contend that if there is an arms race in space, it will be far cheaper to develop offensive weapons than defensive ones. "Chinese strategists consider U.S. reliance on communications, reconnaissance and navigation satellites as a potential Achilles' heel," Maj. Mark A. Stokes, a Pentagon expert on China who was assistant air attache in Beijing from 1992 to 1995, wrote last year. Stokes said Chinese aerospace officials have argued that an anti-satellite capability is "easier to develop than ballistic missile defense systems." The cost to China, he estimated, would be about $30 million for ground facilities and roughly $4 million per interceptor that could destroy a $1 billion U.S. missile defense satellite.

The Soviet Union, which first tested an ASAT in 1968, developed a workable version by the mid-1980s, although it was limited to attacking low-orbit satellites. A comparable American ASAT, launched from an F-15 fighter, consisted of a miniature homing device on a two-stage rocket that used ground-based radar directions to hit the target satellite. As recently as in the 1980s, scientists were also considering so-called space mines -- satellites containing explosives that could be placed in orbit, maneuvered and detonated from Earth.

Air Force Gen. Ralph E. Eberhart, head of the U.S. Space Command, told the Senate Armed Services Committee last spring that "the dependence of our national security on orbiting satellites" makes them "a tempting target for terrorism and adversarial military operations." Eberhart's predecessor at Space Command, Gen. Richard B. Meyers, also said last year that several countries were developing satellite-blinding lasers, missiles capable of dispersing shrapnel in the path of satellites and jammers to foil the U.S. Global Positioning Satellite system, which has both military and commercial uses. "We are going to have to protect our assets in space," Air Force Chief of Staff Gen. Michael E. Ryan told reporters last summer. "In the next 25 years, I see us moving into a substantial defensive requirement in space."