National security adviser Brent Scowcroft denied a report Sunday that U.S. intelligence officials know who carried out the bombing of Pan Am Flight 103.

Appearing on CBS' "Face the Nation," Scowcroft said, "We are not that far along" in the investigation of the Dec. 21 bombing of the jet, which broke apart over Lockerbie, Scotland, killing 270 people.The Sunday Times of London reported that an extremist Palestinian faction financed by Iranian radicals is alleged to have carried out the bombing of Pan Am Flight 103, and U.S. intelligence knows where the bombers are.

The newspaper quoted unidentified sources in Washington as saying the Popular Front for the Liberation of Palestine-General Command made and planted the bomb on behalf of Iranians seeking revenge for the U.S. Navy downing of an Iranian civilian jetliner over the Persian Gulf on July 3. All 290 people on board the Iranian plane were killed.

The newspaper quoted one source as saying the Palestinian group was paid $10 million to destroy the New York-bound Pan Am jumbo jet.

The organization is led by Ahmed Jibril, a Palestine Liberation Organization renegade who opposes PLO chief Yasser Arafat's drive for peace negotiations with Israel.

Scowcroft said there was "a marvelous bit of detective work going on in this whole thing . . . (but) So far as I know, yes, we do not know specifically who did it."

"As far as I know, we are narrowing it down significantly, but I don't know that there is a resolution," Scowcroft said.