Tehran has enjoyed observer status in the Shanghai Cooperation Organisation (SCO) since 2005, but has repeatedly pressed its case for full membership. The organisation's two centres of power disagree over Iran's position: Moscow supports Iranian accession but Beijing seemingly opposes such a move. Iran shares with the SCO the ambition to challenge US dominance and the Western-led order. For Iran, the SCO is also the closest it has to an international defence bulwark, since it is not a member of any other regional security organisation.
