Tehran, which currently holds observer status in the alliance, has long sought to become a full member of the SCO, a security alliance which comprises Russia, China and four Central Asian states and is seen as a counterbalance to U.S. and NATO influence in Asia.

"The consideration of the bid [by Iran] will depend on a political decision on whether to expand our organization," Secretary General Bolat Nurgaliyev said during a Moscow-Beijing video conference hosted by RIA Novosti.

He said Iran’s request has already been addressed to Tajikistan, which currently presides over the organization. The other three Central Asian members are Kyrgyzstan, Kazakhstan, and Uzbekistan, Kazinform cites RIA Novosti.

Nurgaliyev said several other countries are also considering joining the organization. "We see this as positive evidence that our organization is needed and participation in its activities is useful."

He said there are no timelines for SCO accession set out in the organization’s documents, but that there are differences among member states on the issue of expansion.

"The issue of SCO expansion is important to us, and our organization is open to cooperation with other organizations and associations, but maintaining its efficiency must remain the key factor while considering bids for SCO membership," the secretary general said.

Mongolia received observer status in 2004, and India, Iran and Pakistan followed suit in 2005. Besides Iran, Pakistan has also been lobbying for full membership.

The bloc - which primarily addresses security issues but has recently moved to embrace energy projects - has indefinitely postponed accepting new members, but pledged closer cooperation with the observer states.

Speaking at the SCO summit in Kyrgyzstan in August 2007, Russian Foreign Minister Sergei Lavrov said, "Everyone agreed that the moratorium should be preserved for some time yet," adding that the alliance "agreed to involve observer states more actively in practical projects."

The issue of SCO expansion will be on the agenda of an expert-level forum in Beijing in May. "I think recommendations by experts and political analysts will be precious for determining our approaches to this issue," Nurgaliyev said.

Russia and China have been cautious over admitting Iran, embroiled in a long-running dispute with the West and Israel over its controversial nuclear program and alleged support for radical groups in Lebanon and other countries.

Both China and Russia have, however, major commercial interests in Iran. The energy-hungry Asian giant wants Iranian oil and gas and to sell weapons and other goods to the country. 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.

The SCO Council of Heads of State will hold a regular meeting in Dushanbe, the capital of Tajikistan, in August this year. The summit will gather leaders of Russia, China and four ex-Soviet Central Asian states. Representatives of Iran, India, Mongolia, and Pakistan, as well as Afghanistan and some other states will also attend the meeting.

"The documents for the summit in Dushanbe are being prepared, and the final agenda will be approved in Tajikistan at a meeting of SCO foreign ministers in July," Nurgaliyev said.