Defense Secretary Donald Rumsfeld long has pushed for technology that could be used to attack or defend orbiting satellites as well as a costly program, heavily reliant on space-based sensors, to thwart incoming warheads.

Under a 1996 space policy adopted by then-President Bill Clinton that remains in effect, the United States is committed to the exploration and use of outer space "by all nations for peaceful purposes for the benefit of all humanity."

"Peaceful purposes allow defense and intelligence-related activities in pursuit of national security and other goals," according to this policy. "Consistent with treaty obligations, the United States will develop, operate and maintain space control capabilities to ensure freedom of action in space, and if directed, deny such freedom of action to adversaries."

No country depends on space and satellites as its eyes and ears more than the United States, which accounted for as much as 95 percent of global military space spending in 1999, according to the French space agency CNES.

"Yet the threat to the U.S. and its allies in and from space does not command the attention it merits from the departments and agencies of the U.S. government charged with national security responsibilities," a congressionally chartered task force headed by Rumsfeld reported 10 days before Bush and he took office in 2001.

Theresa Hitchens of the private Center for Defense Information said the capabilities to conduct space warfare would move out of the realm of science fiction and into reality over the next 20 years or so.

"At the end of the day it will be political choices by governments, not technology, that determines if the nearly 50- year taboo against arming the heavens remains in place," she concluded in a recent study.

Outlining his election-year vision for space exploration last week, Bush called for a permanent base on the moon by 2020 as a launch pad for piloted missions to Mars and beyond.

One unspoken motivation may have been China's milestone launch in October of its first piloted spaceflight in earth orbit and its announced plan to go to the moon.

"I think the new initiative is driven by a desire to beat the Chinese to the moon," said John Pike, director of GlobalSecurity.org, a defense and space policy research group.

Among companies that could cash in on Bush's space plans are Lockheed Martin Corp., Boeing Co. and Northrop Grumman Corp., which do big business with the National Aeronautics and Space Administration as well as with the Pentagon.

The moon, scientists have said, is a source of potentially unlimited energy in the form of the helium 3 isotope -- a near perfect fuel source: potent, nonpolluting and causing virtually no radioactive byproduct in a fusion reactor.

"And if we could get a monopoly on that, we wouldn't have to worry about the Saudis and we could basically tell everybody what the price of energy was going to be," said Pike.

Gerald Kulcinski of the Fusion Technology Institute at the University of Wisconsin at Madison estimated the moon's helium 3 would have a cash value of perhaps $4 billion a ton in terms of its energy equivalent in oil.

Scientists reckon there are about 1 million tons of helium 3 on the moon, enough to power the earth for thousands of years. The equivalent of a single space shuttle load or roughly 30 tons could meet all U.S. electric power needs for a year, Kulcinski said by e-mail.

Bush's schedule for a U.S. return to the moon matches what experts say may be a dramatic militarization of space over the next two decades, even if the current ban on weapons holds.

Among other things, the Pentagon expects to spend at least $50 billion over the next five years to develop and field a multi-layered shield against incoming missiles that could deliver nuclear, biological or chemical weapons.

Ultimately, this shield -- first proposed by President Ronald Reagan and dubbed "Star Wars" by critics -- may include space-based interceptors, the first weapons in space, as opposed to sensors that guide weapons.

Last year, the Pentagon's Missile Defense Agency obtained $14 million for research on basing three or more missile interceptors in space by the end of the decade for tests.

The plan would field satellites armed with multiple "hit-to-kill" interceptors capable of destroying a ballistic missile through a high-speed collision shortly after its launch, according to Wade Boese, research director of the private Arms Control Association. Such a system could also function as an anti-satellite weapon.