India became more actively involved in the late 1980s, and on 5 June 1987 the Indian Air Force airdropped food parcels to Jaffna while it was under siege by Sri Lankan forces. At a time when the Sri Lankan government stated it was close to defeating the LTTE, India dropped 25 tons of food and medicine by parachute into areas held by the LTTE in a direct move of support to the rebels. Negotiations were held, and the Indo-Sri Lanka Peace Accord was signed on 29 July 1987 by Indian Prime Minister Rajiv Gandhi and Sri Lankan President Jayewardene. Under this accord the Sri Lankan government made a number of concessions to Tamil demands, including devolution of power to the provinces, a merger—subject to later referendum—of the northern and eastern provinces into a single province, and official status for the Tamil language (this was enacted as the 13th Amendment to the Constitution of Sri Lanka). India agreed to establish order in the north and east through the Indian Peace Keeping Force (IPKF) and to cease assisting Tamil insurgents. Militant groups including the LTTE, although initially reluctant, agreed to surrender their arms to the IPKF, which initially oversaw a cease-fire and a modest disarmament of the militant groups.