The protocol on amendments to the treaty was signed by Russian President Vladimir Putin and his Kazakh counterpart Nursultan Nazarbayev after talks in the Kazakh capital, Astana.

The sides also agreed to step up efforts to expand bilateral cooperation and integration.

Moscow and Astana are planning to increase trade from the current $24 billion to $40 billion annually over the next few years.

Nazarbayev said the sides would focus on cooperation in the energy sector, nuclear and space industry, and exploration of resources in the Caspian Sea.

Russia and Kazakhstan have adopted a special statement on preserving the infrastructure of the Baikonur Space Center, which the Russian Space Agency Roscosmos uses to launch various spacecraft into orbit.

Nazarbayev also confirmed plans to build a nuclear power plant in Kazakhstan with Russia’s assistance.

Kazakhstan has tried to balance relations with Russia and the West since becoming independent after the collapse of the Soviet Union in 1991.