Even as tensions lessened and leaders on both sides adopted more conciliatory attitudes, the border issue remained unresolved. Despite their view of the previous border treaties as unequal ones, Chinese leaders were willing to negotiate on the basis of the modern boundaries. That left about 35,000 km² of territory in dispute, with about 28,000 km² in the Pamir Mountains of Tajikistan, 6,000 km² elsewhere along the western border, and about 1,000 km² along the Argun, Amur, and Ussuri rivers on the eastern border. Border negotiations were eventually resumed in 1987 at Mikhail Gorbachev's initiation. An agreement was reached on the eastern portion of the border on May 16, 1991, several months before the final dissolution of the USSR. Russia inherited most of the former Sino-Soviet border, and ratified the agreement in February 1992, while the other post-Soviet republics negotiated separate border agreements.