((a)) The Secretary may establish grazing districts upon any public lands outside of the Aleutian Islands Reservation, national forests, and other reservations administered by the Secretary of Agriculture and outside of national parks and monuments which, in his opinion, are valuable for the grazing of livestock. Such districts may include such areas of surveyed and unsurveyed lands as he determines may be conveniently administered as a unit, even if such areas are neither contiguous nor adjacent.

((b)) The Secretary, after the establishment of a district, is authorized to lease the grazing privileges therein in accordance with the provisions of this subchapter.