The West insisted on this because it feared independence would lead to union with neighbouring Albania and possibly to trouble with Albanian- majority districts in western Macedonia. Those worries were fed by KLA statements last year, which said it would fight for the liberation of all Albanian-majority territory in the Balkans.
For that reason Nato has kept its distance from the KLA and is not supplying it with arms. It would rather defeat Serbia on its own and put alliance troops into Kosovo than see the KLA fill the void.
Since Serbia started its offensive in March the chances of a KLA military victory have looked slim. But the desire for a united "Greater Albania" has probably grown.