The pledge was given by Hashim Thaqi, one of the KLA leaders, to the United States Secretary of State, Madeleine Albright, in Cologne.
Under a peace deal agreed by President Slobodan Milosevic of Yugoslavia, about 40,000 troops are expected to pull out of Kosovo.
Ms Albright confirmed that she had received the assurance from the KLA during a two-hour meeting with Mr Thaqi and other political representatives of Kosovo's Albanian community, Ibrahim Rugova and Rexhep Qosja. The KLA also promised to give up its military functions once the international peacekeeping force moved into Kosovo to take the place of withdrawing Serbs, said Ms Albright.
"Representatives of the Kosovo political leadership have told me without any ambiguity that they will meet the key commitments made at Rambouillet," she said, referring to international talks on Kosovo's future in March. "The KLA will demilitarise and enter into a process of transformation. Kosovo's political leaders will, I hope, co-operate to make Kosovo truly democratic."
Mr Thaqi, head of the KLA's political department, said the KLA planned to change into a "political entity".
The statement was intended primarily to reassure the KLA's Western friends that the organisation would not take advantage of Belgrade's retreat to embarrass Nato by shooting at withdrawing Serbs.
It also confirms what most observers have long expected - that the liberation movement intends to dominate Kosovo's political landscape once the fighting is over and displace the discredited old parties, such as Mr Rugova's Democratic League of Kosovo.
The draft UN Security Council resolution now under discussion in Cologne leaves the political future of the province open. "We are not here to take anybody's dreams away," said Ms Albright cautiously. "The resolution will have language about a political process that will describe how the final status of Kosovo will be achieved."Reuse content