WASHINGTON, Oct 30: The US Air Force quietly has put into service a new weapon designed to jam enemy satellite communications, a significant step toward US control of space.

The so-called Counter Communications System was declared operational late last month at Peterson Air Force Base in Colorado Springs, the Air Force Space Command said on Friday in e-mailed replies to questions from newsmen.

The ground-based jammer uses electromagnetic radio frequency energy to knock out transmissions on a temporary and reversible basis, without frying components, the command said.

"A reversible effect ensures that during the time of need, the adversary's space-based capability to threaten our forces is diminished," said Capt. Angie Blair, a spokeswoman. "Following the time of need, the space-based capabilities used by the adversary can return to its original state."

The device appears to have been put into service considerably earlier than had been projected by the Air Force as recently as February.

At that time, a long-range planning document, dubbed the Transformation Flight Plan, said such a system would let the United States by 2010 "deny and disrupt an adversary's space-based communications and early warning" of attack.

US military control of space is one of four missions spelled out under a national space policy adopted by former president Bill Clinton in 1996. The goal is to make sure US forces have unhindered access to space and space-based services and to deny an enemy any similar benefits.

The US military has experimented with a range of "anti-satellite" (ASAT) weapons, including lasers, to knock out enemy craft by destroying them or damaging their sensors.

Theresa Hitchens, vice president of the private Center for Defence Information in Washington, welcomed the new system on the ground it would not create debris that could threaten global use of space and would not destroy satellites, only jam them temporarily.

"Unfortunately, it seems we are not going to limit our quest for 'space control' to benign systems," she said, citing the danger of a space arms race.

The deployment was disclosed without fanfare late last month at a technical conference of the American Institute of Aeronautics and Astronautics in San Diego, California.

The system is operated by the 76th Space Control Squadron, a unit created in 2001 to explore technologies for controlling space, Brig. Gen. Larry James, vice commander of the Space and Missile Systems Command told the conference.

The Air Force Space Command, in its e-mailed replies, said the system was built from off-the-shelf commercial equipment, and made up an antenna, transmitters and receivers that can be loaded into a trailer and moved from place to place.

Three such systems had been delivered since late last year, the command said. The program's budget for fiscal 2005 totalled 6.2 million dollars, according to the Congressional Research Service.-Reuters