The officer is the first member of the Yugoslav military to become a prisoner of war during the campaign.

Reports say he is being interrogated by the Pentagon.

But Nato spokesman Jamie Shea said on Saturday he would not be used for propaganda.

Nato spokesman Jamie Shea: He will be treated very humanely

The officer, aged about 20, was in good condition with food and shelter, added Mr Shea. He would be protected by the Geneva Convention and would have access to mail and the right to make a complaint.

Mr Shea said he did not know why the prisoner had been given to the Americans, but added: ''He will be treated according to the most humane conditions, in the most civilized fashion.

"He's probably going to be much better looked after and much better cared for in his current situation than where he was three or four days ago."

The prisoner was seized by the KLA near Junik, close to the Albanian border, on Tuesday night or early Wednesday.

He was delivered to the Albanian Government on Friday, which turned him over to the US.

Yugoslav forces two weeks ago captured three American soldiers near the Macedonia border and are holding them as PoWs.

It is not yet known whether the US will propose a prisoner exchange.

'Soldier won't be named'

In Washington, Pentagon spokesman Mike Doubleday said the soldier was in the Prva Drugi battalion commanding about 20 men.

He was involved in an operation against the KLA in an area where there are about 400 Yugoslav Army soldiers and security police.

Captain Doubleday said the soldier had been seen by the International Committee of the Red Cross and been allowed to write to his family. The ICRC has not been given access to the captured US servicemen.

The Pentagon said the soldier would not be named and would be repatriated immediately after hostilities ended.

Mr Shea added that it was not a coincidence that the soldier was seized in the same area where Nato accidentally bombed a convoy of refugees.

''This is the area where Yugoslav forces have been operating. They're trying very hard to push the KLA back from the Albanian border and that's the region where a lot of ethnic cleansing has taken place.

''This is the area where thousands of people are currently being forced out of their homes which are then systematically looted and burned by the Serbs.''

'Ground war hotting up'

Nigel Vinson of the Royal United Services Institute said it appeared the rest of the officer's force had been killed.

He said there were about 2,000 KLA fighters in the area where the soldier was seized.

''What this probabaly indicates is that the war on the ground is now hotting up,'' he added.

''The KLA in the last week or so has had large reinforcements as the ethnic Albanians have been pushed out of Kosovo ... and what we now see is a renewed campaign by the KLA.''