At least a dozen Yugoslav tanks and numerous armoured vehicles left fortified positions north of Pristina on Saturday, apparently heading back to barracks.

Listen to Paul Wood's report

They had been sent out last week to guard the main road into Kosovo from Serbia proper in an area where the rebel Kosovo Liberation Army (KLA) has been especially active.

Their withdrawal now might be seen as a result of the increasingly tough Western rhetoric about air strikes, but it has emerged that the pullback was able to go ahead because of a series of local ceasefires being organised by the Kosovo diplomatic observer mission, which predates the OSCE monitoring task force currently setting up in the province.

In the case of the deployment north of Pristina, KLA commanders have told me that they have agreed to allow Serbian forces free movement on the main road as long as the Yugoslavs don't come into Albanian villages nearby.

KLA: Struggle will go on

The deal - confirmed by Western diplomatic sources - was brokered with the help of the KLA's political representative, Adem Demaci, and British and American diplomatic observers.

However the arrival of more monitors would "absolutely not" mean the end of the armed struggle, according to the KLA commander with responsibility for the area where Saturday's withdrawal of Yugoslav forces took place.

"We took up arms and we're not going to put them down. Every day we are much stronger, and in the end we will control all the territory of Kosovo."

This secret mediation effort by the Kosovo diplomatic observers represents a major departure from the original mission of simply logging troop movements and reporting back to Western governments.