A senior American official said today that the United States had never intended to insist that "that every single Serbian weapon is put in a pen somewhere."

Serbian secret weapon (antiwar aphorisms and cartoons, Serbia, Belgrade 2005. )

So a swift use of NATO air power to keep Sarajevo and Gorazde clear of Serbian heavy weapons is expected.

My mission," he said, "is to survey the Serbian weapons and prevent any use of them.

He added that "more than 50 percent" of Serbian heavy weapons had been withdrawn beyond the zone, rather than placed under United Nations control.

But journalists in the Serbian-controlled hills have steadily been discovering clumps of Serbian weapons, some deserted, others fully manned.

One fear is that the withdrawal of Serbian heavy weapons will relieve Muslim defenders, who could then fight the Croats farther west.

A senior NATO diplomat said bombs could start falling even if only a few Serbian weapons were not withdrawn by Sunday night.

In particular, he referred to a concentration of Serbian heavy weapons near the airfield where United Nations planes are landing.