The $250m Defence Support Programme satellite went up without a hitch from Cape Canaveral on Friday on board the unmanned Titan 4B rocket.

But a spokeswoman for the satellite's control centre at Schriever Air Force Base in Colorado said: "The satellite was not placed in its required geosynchronous orbit."

Titan 4A explodes to the tune of $1bn

She said two rocket firings required to position the satellite did occur but it had still failed to find its correct orbit 19,320 miles above the equator.

It is now travelling on an egg-shaped loop around Earth.

The spy satellite and its rocket together are estimated to have cost about $682m.

The latest mishap follows an explosion that destroyed the latest rocket's predecessor, Titan 4A, and its satellite cargo shortly after launch last August.

Archive of last August's explosion

That accident was estimated to be one of the most expensive space disasters yet, costing approximately $1bn.

Schriever Air Force Base said it was "looking at every angle possible to see what can be done to salvage the satellite".

Similar satellites have been watching over the Balkans as Nato conducts air strikes against Yugoslavia. The network was also used extensively during the Gulf War to spot Iraqi Scud missile launches.