White House and Pentagon officials described as premature published reports that the United States will break the SALT II treaty limits this week. The reports said that the 131st B-52 bomber in the U.S. fleet will be armed this week with a nuclear cruise missile and become operational, a move that would exceed the limits of the unratified 1979 strategic arms limitation treaty. Pentagon spokesman Robert Sims said it is "no secret" that such a move will be made later this year but said the reported timetable is premature. White House spokesman Larry Speakes said he believes there will be no deployment until December. Citing Soviet treaty violations, President Reagan announced in May that he would no longer abide by SALT II.