The British government is expected to charge an army major with providing classified NATO information and documents to the Bosnian Serb leadership during the past two years of the Balkan war, according to senior Western diplomats.

In a case compiled in part by U.S. intelligence officials, the major, Milos Stankovic, 35, is said to have seriously undermined the effectiveness of the U.N. peacekeeping effort in Bosnia, the diplomats said.He is said to have kept the Bosnian Serb military commander, Gen. Ratko Mladic, who has been indicted on two counts of genocide by the international war-crimes tribunal in The Hague, Netherlands, abreast of top-secret NATO plans and procedures and of the bickering within NATO during the 1992-95 war.