The Islamic Republic, which currently holds an observer status in the regional security group, has long sought to become a full member of the SCO, seen as a counterbalance to U.S. and NATO influence in the region.
The bloc - which primarily addresses security issue but has recently moved to embrace energy projects - has indefinitely postponed accepting new members, but pledged closer cooperation with the observer states.
Both China and Russia have, however, major commercial interests in Iran. The energy-hungry Asian nation wants Iranian oil and gas and to sell weapons and other goods to the Islamic Republic. Moscow also hopes to sell more weapons and nuclear energy technology to Tehran. The Kremlin also needs Iran's endorsement for a multinational arrangement to exploit the Caspian Sea's energy resources.