Following intense western sanctions in the wake of Russia's invasion of Crimea, Beijing upped its economic support for Moscow, and both countries have long supported each other at the United Nations on issues such as North Korea and Syria, where they are in opposition to or disagreement with the US.

Both countries have urged the US to suspend military exercises on the Korean Peninsula as a show of good faith to North Korea and move towards denuclearization.

At a UN meeting in September, the foreign ministers of both countries criticized Washington for its aggressive stance in global affairs, and said we were seeing a transition to a "multipolar world" without a single superpower.

The SCO is a major part of that multipolarity. A grouping of China, Russia, Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, India and Pakistan, it has been compared to an eastern NATO, and is designed in part to counterbalance western influence in Asia and the Middle East.

According to Chinese state media, the June summit is intended to make the organization "more cohesive, effective and influential," in part by building on China's activity in promoting its Belt and Road economic project, which includes a broad swath of central and southeast Asia and parts of Africa, and has been accused of being "neo-imperialist."

Through the SCO, regional military leaders often meet to discuss security issues, such as separatism, terrorism and extremism.

A key area where the SCO has been influential worldwide is in promoting so-called cyber sovereignty, the idea that states should be able to police their digital borders as they do physical ones with widespread censorship and content filtering. SCO members have attempted to water down international protections for freedom of speech and throw out current rules on how domain names are issued.