BROYE-LES-PESMES, France - A French space-surveillance radar has detected 20-30 satellites in low Earth orbit that do not figure in the U.S. Defense Department?s published catalogue, a discovery that French officials say they will use to pressure U.S. authorities to stop publishing the whereabouts of French reconnaissance and military communications satellites.

After 16 months of operations of their Graves radar system, which can locate satellites in orbits up to 1,000 kilometers in altitude and even higher in certain cases, the French Defense Ministry says it has gathered just about enough information to negotiate an agreement with the United States.

The U.S. Defense Department?s Space Surveillance Network is the world?s gold standard for cataloguing satellites and debris in both low Earth orbit and the higher geostationary orbit at 36,000 kilometers in altitude, where telecommunications satellites operate.

Data from the U.S. network of ground-based sensors is regularly published and used worldwide by those tracking satellite and space-debris trajectories. The published U.S. information excludes sensitive U.S. defense satellites, but regularly publishes data on the orbits of other nations? military hardware.

In a series of presentations here at the site of the French Graves radar facility, French defense officials said they are gathering data on classified satellites in low Earth orbit as part of a future European space-surveillance program that European Space Agency governments will be asked to approve in 2008. This program, with a cost of some 300 million euros ($405 million), would feature higher-performance radars to track space debris in low orbit and in geostationary orbit.

This new space surveillance program may or may not be approved by European governments. But the Graves radar, and a complementary system operated by the German government, together already are enough to pinpoint the location, size, orbit and transmissions frequencies of satellites that the United States would prefer not be broadcast worldwide, French officials said.

?We have discussed the Graves results with our American colleagues and highlighted the discrepancies between what we have found and what is published by the U.S. Space Surveillance Network,? said one French defense official responsible for the Graves operation. ?They told us, ?If we have not published it in our catalogue, then it does not exist.? So I guess we have been tracking objects that do not exist. I can tell you that some of these non-existent objects have solar arrays.?

Col. Yves Blin, deputy head of the space division at the French joint defense staff, said France would wait until it had acquired, with the help of the German radar, further information about the 20 to 30 secret satellites in question before beginning serious negotiations with the United States on a common approach for publishing satellite orbit information.

?Right now we do not have enough cards in our hand to begin negotiatons,? Blin said here at the Graves radar transmitter site June 7. ?We need more time to be sure of what we are seeing. At that point we can tell our American friends, ?We have seen some things that you might wish to keep out of the public domain. We will agree to do this if you agree to stop publishing the location of our sensitive satellites.?