With their three-decade tussle for leadership of the communist world - including a fateful clash on the Ussuri River in 1969 - a distant memory, Sino-Russian ties have shown remarkable advances in recent years.

The land border was settled in 1991, mutual troop reductions along the frontier followed and an arms trade began, highlighted by the landmark Chinese purchase of the Su-27 fighter that was denied at the time even to Warsaw Pact allies, who had access only to the less sophisticated MiG-29.