Technicians at a remote Army base in the New Mexico desert are several days away from firing a powerful laser at an aging Air Force satellite in the first simulated attack by such a futuristic weapon on Earth against a satellite in space, the Defense Department announced yesterday.

Defense Secretary William S. Cohen approved the test while traveling in Europe yesterday, over concerns by officials at the State Department, Democratic leaders in Congress and some commercial satellite manufacturers who worry that the test may undermine current arms control efforts or launch a race for new antisatellite weapons.

Pentagon officials said the laser firing is designed to yield a greater understanding of how to protect U.S. satellites from such attacks. But officials acknowledged the test also will provide data the Army can use to refine the laser for use in a future military conflict or to develop additional lasers for antisatellite use, fulfilling a cherished Defense Department goal dating from the heyday of futuristic weapons testing in the mid-1980s under the "Star Wars" program.

Critics of the test are principally concerned that any demonstration of a U.S. laser capability to damage satellites in space will encourage other nations to develop antisatellite weapons. At present, only Russia is believed to have a laser in the same class as the Army's, although U.S. intelligence officials worry that China and perhaps Iraq eventually may try to develop one.

The target is a satellite launched in May 1996 to survey Earth's surface with infrared sensors, which the Air Force says has outlasted its projected lifespan. Its orbital altitude is roughly 263 miles, slightly less than the orbital range occupied by more than 30 U.S. commercial communications satellites and projected to be filled by 100 such satellites by the end of the decade.

Clay Mowry, who directs the Satellite Industry Association in Alexandria, said executives at some of the 18 major aerospace firms in his group are worried that the test could set a dangerous precedent and promote development of foreign lasers that ultimately could threaten commercial satellites now producing an estimated $23 billion in revenue annually.

"Does this put down a marker that people can start doing this to someone's commercial business in space?" Mowry asked, noting he was not speaking for the association's board. "Some companies have concerns over when and how this technology might be used. But no one from the Pentagon has called in the commercial industry to talk . . . about their plans or find out where they might be on this issue."

The laser facility at the heart of the test was developed for $800 million on a remote portion of the White Sands Missile Range. Its initial goal was to help the Navy design a weapon to shoot down cruise missiles headed for its ships, but its mission was diverted in 1983 to help develop advanced weaponry that might shoot down enemy missiles or incoming nuclear warheads as part of President Ronald Reagan's "Star Wars" program.

The laser, which produces a focused beam of intense energy measuring roughly five to six feet across at its source, is no longer regarded as an effective ground-based weapon against warheads or a possible space-based weapon against missiles. As a result, the Pentagon repeatedly has attempted to cut its budget, only to be rebuffed by New Mexico lawmakers who insisted that the facility be kept active, according to the trade publication Inside Missile Defense.

The Army originally sought to conduct the test before the end of the fiscal year that ended Sept. 30, using funds from a $1 million budget for experimentation. But approval was delayed several weeks while the plan was subjected to extra scrutiny by Cohen and other senior policymakers.

Speaking yesterday in Maastricht, Netherlands, after a meeting of NATO defense ministers, Pentagon spokesman Kenneth Bacon said the aim of the test will be "to reduce the vulnerability of U.S. satellite systems" by measuring how readily the device can damage the target satellite. He emphasized it will violate no arms treaties or international agreements.

But in internal administration deliberations, some State Department officials expressed a concern that "nothing good will come of [the test] from a diplomatic perspective," said one official, who asked not to be named. He said the officials worried in particular about repercussions in Russia, where legislators have balked at ratifying the START II arms reduction treaty.

"There are no active programs with an antisatellite potential or aim" anywhere else in the world, the official said, a circumstance that he said suggested the Pentagon's anxieties are unwarranted. Some critical U.S. military satellites have already been hardened to protect against possible attack by ground-based lasers, other officials said.

Pentagon spokesman Bob Potter said he was unaware of any other nation with a ground-based laser comparable to the so-called Mid-Wave Infrared Chemical Laser (MIRACL) in New Mexico, but noted that "a lot of countries lase satellites" with lower-powered beams to track their trajectory.

Protests against the test were made last week by House Minority Leader Richard A. Gephardt (D-Mo.) and the senior Democrats on the House Budget and National Security committees, John M. Spratt Jr. (D-S.C.) and Ronald V. Dellums (D-Calif.). In a joint letter to President Clinton, they complained that "we know of no hearings, briefings, or consultation with members of Congress" about the test.

Senate Minority Leader Thomas A. Daschle (D-S.D.) and the ranking Democrat of the Senate Armed Services Committee, Carl M. Levin (D-Mich.), also objected to the test, while Sen. Tom Harkin (D-Iowa) wrote his own letter of protest to Clinton, according to several sources. Sen. Jeff Bingaman (D-N.M.) said in a statement yesterday that he hoped the test would accomplish its objectives, but also urged the administration to consult with Russia and said conducting such tests "on the basis of opportunity is not the wisest way to proceed."

In the test, which Pentagon officials said will not be visible to any onlookers and must be conducted in clear weather, the laser will be fired once for less than a second to help point it at the target and a second time for less than 10 seconds to measure the beam's power. "It doesn't destroy the satellite, doesn't create any debris, and it does not pose any risk to other satellites," spokesman Michael Doubleday said.

The challenge for laser engineers will be to keep the beam focused on the satellite-roughly the size of a small refrigerator-while it travels through space at an estimated speed of 16,664 mph, officials said. A major question is how much the atmosphere will distort the beam before it reaches the target.