The data, normally released as part of the civil space agency's Orbital Information web page, and the Spacewarn Bulletins, will be withheld "until further notice", due to the fact that many of the military satellites were now deemed critical to US-NATO military operations in Yugoslavia, press reports in Washington suggested.

But the effect of the decision is to draw an even starker contrast around the fact that space assets are clearly now considered critical to U.S. military operations.

U.S. Space Command, Colorado Springs, Colorado, made the decision that took effect March 1st, according to a Washington Post newspaper story. While the data was not considered classified information, any hostile force that wished to disrupt military communications, weather plotting, or mobile Internet and email for U.S. and allied forces could easily know when such satellites were within the sphere of activity or in range of forces or ground stations.

Such tracking location information, on all 600 U.S. Earth-orbiting spacecraft, has been routinely published by NASA since the start of the Spacewarn program. The web site was launched in 1996. Now, and possibly even after the end of hostilities in Bosnia, the tracking data on military satellites will only be available on what was described as a "need to know" basis-and possibly during certain periods, outside of defense or intelligence community circles.

Included in the ban will be the Air Force's Global Positioning System navigation satellites, military communications satellites used by the Navy, early warning missile threat alert satellites in the Defense Support Program, and military weather satellites. Satellites that are primarily civil or commercial in nature but which sometimes carry military data will not be effected, sources said. NASA will also continue to publish Space Command data on space debris and related object tracking information.