U.S. Probes Intelligence on Missiles in Bosnia : Balkans: Inquiry asks whether SA-6 weapons were detected but no warning relayed before F-16 was shot down.

The Clinton Administration said Sunday it is looking into whether U.S. intelligence agencies discovered SA-6 missiles in northwestern Bosnia-Herzegovina a day before an American F-16 was shot down there but failed to pass the information on to commanders in the field.

Senior Administration officials said the Pentagon and the CIA are conducting separate investigations of the incident and hope to have a firm answer in a few days.

Last week, top military officials asserted that U.S. commanders had not known that the Bosnian Serbs had portable missile launchers in the region and thus did not send escort planes with the F-16.

Almost immediately after the F-16 was shot down, U.S. Navy Adm. Leighton W. Smith, commander of NATO forces in southern Europe, ordered that radar-jamming planes and missile-destroying aircraft accompany any U.S. or allied air patrols over Bosnia.

Air Force Capt. Scott F. O’Grady, the pilot of the downed F-16 who was rescued early Thursday after spending nearly six days hiding from Bosnian Serb forces, arrived at Andrews Air Force Base outside Washington on Sunday. He will meet today with President Clinton.

The SA-6 is a Soviet-made surface-to-air missile that is mounted on a pair of tank-like vehicles and can be transported without being readily detected. One vehicle carries the launcher and missiles, and the other holds the radar system.

Leon E. Panetta, Clinton’s chief of staff, said the White House has ordered a full probe of the circumstances surrounding the shoot-down. “I don’t know what exactly happened in this instance,” he said on NBC-TV’s “Meet the Press,” but “we’re looking into the situation to make sure that it doesn’t happen again.”

An article in the Washington Post quoted Pentagon sources as saying that, the day before O’Grady’s jet fighter was shot down over Bosnia, U.S. intelligence equipment detected at least one surface-to-air missile system in the area but that the information was not passed on to the pilot’s commander.

The story said the National Security Agency, which gathers intelligence through electronic means, had detected a tracking radar for the SA-6 missile, but the report implied that the information was not disseminated to field commanders.

Both Pentagon and intelligence officials cautioned Sunday that they have no evidence so far to suggest that the allegations reported in the Post are true. “That . . . is way off from everything I’ve heard,” one well-placed official said.

A spokesman for the NSA said Sunday that it had had “no indications of SA-6 presence prior to June 2,” the date that O’Grady’s F-16 was downed.

The NSA would not elaborate, but a senior Administration official told The Times there were indications that the intelligence agency had received some signs that the Serbs had SA-6 missiles in the area on the morning that O’Grady took off from Aviano Air Base in Italy on his fateful mission, but that the information was vague and not considered very reliable.

He said authorities were trying to determine whether what may appear in retrospect to have been an important piece of information may have been reasonably discounted on the morning of O’Grady’s flight.

Meanwhile, the NSA said the agency was now “engaged in a review to determine how much advance notice was available to warn Capt. O’Grady” on the morning that he began his mission.

The developments came as the U.N. mission in Sarajevo, the Bosnian capital, announced that it will essentially restrict its peacekeeping operations in Bosnia to humanitarian efforts, not military confrontation, to clear the way for new diplomatic efforts to free Serb-held hostages.

In a formal statement, the mission said it will “strictly abide by peacekeeping principles until further notice,” despite the recent announcement by the allies that they plan to send a British-French rapid-reaction force to reinforce U.N. troops.

Bosnian Serb forces shelled two Muslim-held suburbs of Sarajevo on Sunday, and fighting erupted in the Muslim enclave of Gorazde in another violation of the U.N. ban on heavy weapons in protected areas.

Serbian forces still hold about 145 of the nearly 400 U.N. peacekeepers and officials whom they took as hostages following a series of U.S.-engineered air strikes on Bosnian Serb ammunition dumps near Sarajevo last month.

U.S. officials denied that American intelligence agencies had evidence that Serbian President Slobodan Milosevic has continued to provide military aid to the Bosnian Serbs even as he has assured the allies that he has stopped all but non-lethal assistance.

A senior Pentagon official said that, although intelligence agencies have observed signs that there is “some leakage or smuggling, we have no credible evidence of direct involvement by the Serbian government in providing military assistance to the Bosnian Serbs.”

Defense Secretary William J. Perry has noted that U.S. and other North Atlantic Treaty Organization aircraft have flown about 69,000 sorties over Bosnia since the allies decided to impose a “no-fly” zone in the region and have suffered only two shoot-downs--O’Grady’s F-16 and a British Harrier in 1994.