Early extracts from a speech given in the US by Defence Secretary George Robertson said that Nato must keep its options open.

But when the speech was delivered at Harvard University the idea that Allied plans for ground troops must be kept "under review" had been removed.

Defence Secretary George Robertson: "I am not saying that..."

A spokesman said the change was due to the ''pressure of time'' and part of the speech had to be cut.

Mr Robertson said simply that ground troops would be needed as soon as Yugoslav President Slobodan Milosevic had accepted Nato's demands.

The speech extracts, released earlier on Friday, were immediately seen as part of a gradual shift among Nato leaders, who initially ruled out sending in forces when the air strikes began in March.

'Air strikes successful'

Afterwards Mr Robertson was asked on the BBC's Newsnight programme if he had used the phrase "under review''.

He said: "No I did not say that, I'm not saying that in any speech.

"We looked at all of the options at the beginning of this campaign and we decided on air attacks as being the best and most effective way to disrupt the violence going on in Kosovo and to weaken the military machine that was causing that violence.''

Asked if it was inconceivable that grounds troops would go in before President Milosevic surrenders, he said: "Our plans at the moment are quite clearly and specifically related to ground forces going in, in an permissive environment when the air campaign has reduced the military machine which is conducting the killing at the present moment.

"That position has not changed because we took a decision at the beginning that air attacks were the best way of going about it.''

'Invasion not an option'

Prime Minister Tony Blair again insisted that a ground invasion of Kosovo was not an option.

Writing in The Sun newspaper, he said: "We said that in the beginning and that remains the case.

"Even if we'd threatened a ground war at the beginning that would have changed nothing because we would still have been a considerable time from putting one together."

Labour MP Ann Clwyd, who has been touring refugee camps in Macedonia, has repeated her calls for ground troops to be bought in.

"People who are in the Army are trained to kill and, unfortunately, are also trained to be killed," she said.

"To suggest that an Army can't face up to that is ridiculous. I think the British public has shown, through the rise in the number of people in opinion polls who think ground troops should be used, also share that belief."

War crimes job

Meanwhile, Foreign Secretary Robin Cook has appointed a new "war crimes supremo" to gather evidence of Serbian atrocities in Kosovo.

Senior Foreign Office official David Gowan will examine all evidence coming into the UK Government about war crimes to ensure that the international War Crimes Tribunal in The Hague can prosecute Serb military commanders.