WASHINGTON -- The unprecedented downing of an errant spy satellite by a Navy missile makes clear that the Pentagon now has a new weapon in its arsenal: an anti-satellite missile adapted from the nation's missile defense program.

While the dramatic intercept occurred well below the altitude where most satellites orbit, defense and space experts said Wednesday night's first-shot success strongly suggests that the military has the technology and know-how to knock out satellites at much higher orbits.

The Pentagon officials said it was 90 percent certain that the missile had struck its primary target, a tank containing toxic fuel, but they stressed that the shoot-down did not indicate that the United States was actively developing an anti-satellite program.

Gen. James Cartwright, vice chairman of Joint Chiefs of Staff, said the effort was not a test of the nation's missile defense system, nor a show of force to put other countries on notice that the United States can take down a satellite. "This was uncharted territory," he said. "We see this as a one-time event."

Nonetheless, many space experts and arms control advocates in the United States and abroad said the shot had opened the door to more anti-satellite tests by more nations.

"Demonstrably, we do have an [anti-satellite] capability now," said David Mosher, a Rand Corp. defense and space expert. "Anyone who followed national missile defense issues knew we've had that inherent ability for some time. But now it's real, and we can expect there will be consequences."

Clay Moltz, a professor of nuclear and space policy at the Naval Postgraduate School in California, agreed that the satellite's destruction did not signal a new capability, but said it might have sent a signal to other countries that could set a bad precedent

Riki Ellison, president and founder of the Missile Defense Advocacy Alliance, said it was "remarkable" -- and good news -- that the missile defense system is so easily adaptable. "We now have something that has the capability, anywhere around the world, to handle a falling satellite," he said. "The world wasn't really watching it before. This is much more now known throughout the world that we have this capability."

The Chinese Communist Party newspaper condemned what it called Washington's callous attitude toward the weaponizing of space. The Chinese government -- which conducted a full-scale anti-satellite test in January 2007 -- asked the United States to release data on its shoot-down and where the satellite's debris would fall. Defense Secretary Robert Gates said in Honolulu that some information would be shared to assure the Chinese and others that any pieces that reach the surface will not be hazardous.

Many governments accepted the Bush administration's explanation that the satellite had to be attacked because it was carrying a 1,000-pound tank of potentially hazardous hydrazine rocket fuel.

Geoffrey Forden, a Massachusetts Institute of Technology researcher who worked with colleagues to estimate the probability of the hydrazine harming anyone on Earth, said that if the fuel tank made it through the atmosphere, there was a 3-in-100 chance that it would land within 100 yards of someone on the ground. But he and his colleagues also calculated that the tank would be subject to a force of 50 times gravity (at the surface) as it fell through the atmosphere, and there was virtually no chance that it would have remained intact.