The SCO comprises Russia, China, Kazakhstan, Tajikistan, Kyrgyzstan, and Uzbekistan. Russia took over the presidency of the organization last August. Iran, India, Mongolia and Pakistan have observer status within the organization.
"Consideration of Tehran's bid is moving ahead in accordance with standard procedures. I think that a decision on the issue could be announced at a SCO summit in Yekaterinburg [Russia] in June," the source said.
Widely seen as a counterweight to NATO's influence in Eurasia, the group primarily addresses security issues, but has recently moved to embrace economic and energy projects.
The SOC has recently lifted a moratorium on its membership, but has not yet established any criteria for accepting new members, according to a Russian diplomatic source.
Iran's Foreign Minister Manouchehr Mottaki said on Monday that Tehran expected to receive the backing of Russia in its drive to become a SCO member.
However, Russia and China so far have expressed caution over admitting Iran, which is embroiled in a long-running dispute with the West and Israel over its nuclear program and alleged support for radical groups in Lebanon and other countries.
Both China and Russia have major commercial interests in Iran. China wants Iranian oil and gas, and to sell weapons and other goods to the country, while Moscow hopes to sell more weapons and nuclear energy technology to Tehran.