WASHINGTON - The Defence Department announced Monday that it will deploy to Afghanistan by June an aviation brigade from the 82nd Airborne Division. The 2,800-person unit is separate from four ground combat brigades that US commanders said they need in Afghanistan, Pentagon spokesman Bryan Whitman said. The 3,500-person 3rd Brigade Combat Team deploying in January from Fort Drum, New York, will be the start of that build-up. The aviation brigade from Fort Bragg, North Carolina, will provide helicopter reconnaissance and other support for the combat teams and NATO forces, Whitman said. The US has 31,000 troops in Afghanistan, including 14,000 that are part of the 51,000-member North Atlantic Treaty Organization force there.