NATO\'S top official is vigorously defending the alliance\'s plan for a shield against ballistic missiles, despite two US reports which cast doubt on the project\'s technical and financial feasibility. Secretary-General Anders Fogh Rasmussen said in an interview with The Associated Press on Monday that technical tests of the missile defense system for Europe show that it works, and added the alliance will discuss it at a summit in Chicago next month. Reports released by the Defense Science Board, an advisory group to the US Defense Department, and the US Congress\' Government Accountability Office, indicated the system is plagued by technological problems and cost overruns.