At a Pentagon briefing on Saturday evening, a US military spokesman said the pilot whose description of a military strike was released on tape the following day was not, in fact, describing the attack on the refugees.

Pentagon officials have told the BBC that Nato planes attacked three separate convoys around Djakovica on Wednesday and they are now certain that the pilot concerned attacked a purely military convoy.

The announcement has led to renewed confusion over the attacks, in which more than 60 civilians are thought to have died.

The Pentagon has admitted that it made a mistake in releasing the pilot's recording.

BBC Washington correspondent Tom Carver says that the officials have not, however, denied that Nato was responsible for hurting civilians in other attacks on other convoys.

A large number of US F16s were in the area

But our correspondent says that as the majority of Nato aircraft in the area on that day were US F16s, it seems probable it was an American pilot that was involved in the attack on the refugees.

In the recorded debriefing released to the media on Thursday, the unnamed pilot said he made several passes over the convoy "to ensure that they are in fact military vehicles", before dropping a single bomb. He then passed the convoys co-ordinates on to another aircraft which attacked with a laser guided weapon.

His account led to widespread confusion over how an experienced pilot could mistake a convoy of tractors laden with refugees for camouflaged military vehicles.

Investigation continues

Nato meanwhile has said it will not release further information on the attacks until it has had time to carry out further investigations.

Nicholas Witchell: "Nato in a corner over the refugee convoy"

Under repeated questioning on Friday, Nato spokesman Jamie Shea confirmed that a single, laser-targeted bomb dropped by an American F16 hit one civilian target in a convoy travelling north of Djakovica on Wednesday.

He described the destruction of the vehicle, believed to be a tractor, as a "tragic accident", but said a video of the attack would not be released until investigations had been completed.

Heated exchanges at the daily Nato press conference

BBC Defence Correspondent Jonathan Marcus says he understands that Nato's military command had prepared a detailed briefing document but at the last moment, Nato's political authorities refused to allow this to be made public.

Serbian officials in Pristina say the incident took place near Meja, adjacent to Djakovica.

In a second alleged Nato attack, bombs dropped between Djakovica and Prizren to the south are said to have killed six and wounded 11.

The convoy attack left at least 60 dead

Refugee claims that Yugoslav Air Force jets were involved in attacks in the area have not been independently corroborated.

In a third report, refugees said they saw a convoy bombed between Prizren and the town of Morini alouth neither Nato nor the Yugoslav authorities have confirmed this attack.

Mr Shea said Nato "does not accept the blame" for either attack.

'Scepticism' about Serb claims

Yugoslav television has been showing pictures of two separate scenes of what they say are attacks on refugee convoys. One shows a column of destroyed vehicles on a tarmac road and the other on a dirt track.

It was not made clear where either site was located.

The alliance has repeatedly cast doubt on the authenticity of many Serb claims.

Journalists taken by Serbian authorities to the scene of one site, between Prizren and Djakovica, were shown evidence of air strikes but say it is impossible to judge the authenticity of Serb claims.

BBC correspondent Michael Williams, who visited the area between Prizren and Djakovica, said that he had seen the bodies of refugees and four impact craters - suggesting four bombs had been dropped.

This matches eyewitness accounts suggesting more than one bomb was dropped on the convoy.

He said there was no evidence of military vehicles, but that 36 hours had elapsed since the bombing raids allowing plenty of time for the scene to be "doctored".