The Shanghai Cooperation Organisation, meeting in the Russian city of Ufa a day after the BRICS emerging economies held a summit there, said the invitation to the two Asian nations showed a "multi-polar" world was now emerging.

Those words will have pleased Putin, who says the United States has an outdated vision of a "uni-polar" world dominated by Washington and wants to show Russia has not been weakened by Western sanctions over its role in the Ukraine crisis.

"The evolution of the SCO is taking place at a complicated stage in the development of international relations and amidst the emergence of a multi-polar world," the group said in a declaration after the meeting.

"These processes are accompanied by increasing security challenges and threats, increasing uncertainty and instability in various regions of the world."

The SCO, which also includes the Central Asian former Soviet republics of Kazakhstan, Uzbekistan, Kyrgyzstan, Tajikistan, is widely seen as a platform for Moscow and Beijing to project influence in the region.

Until now it has not been a big force and relations between China and Russia have not developed as quickly as Moscow would like, despite agreement on a major gas supply deal last year.

But Putin saw the signs of unity in the SCO and the BRICS - Brazil, India, South Africa, China and Russia - which agreed to coordinate efforts to keep their economies stable, launched a development bank and agreed on a currency pool.

Indian Prime Minister Narendra Modi said the expansion of the SCO should serve a "springboard" for the organization to become one of the most dynamic in the world.

"The time has come to reach out across the region," Modi said. "We have everything we need to succeed."

Pakistani Prime Minister Nawaz Sharif said: "President Putin's efforts will enhance the political and economic scope of the Eurasian belt."

ENERGY PRODUCERS

The addition of Pakistan and India, two nuclear-armed neighbors who have years of tensions between them, could also lead to easing the conflicts between New Delhi and Islamabad.

The two leaders agreed in a separate meeting in Ufa that Modi would visit Pakistan next year.

Joining a group that includes energy producers such as Kazakhstan and Russia may have been a strong incentive for the two countries to join.

"India is particularly interested because it lacks direct access to Central Asia, and it sees SCO membership as a way to get a better foothold on the region. SCO membership could better position India to benefit from Central Asia's gas riches," said Michael Fugleman, senior program associate for South and Southeast Asia at the Wilson Centre in Washington.

But he added: "In (the) SCO, India and Pakistan wouldn't be dominant powers - China and Russia would retain that title."

The SCO did not invite Iran to join, although it has long sought membership. The group says Iran can join only after reaching a deal with big powers on its nuclear program.

With the addition of Iran, the group would control around a fifth of the world's oil and represent nearly a half of the global population. The BRICS account for a fifth of the world's economic output and 40 percent of its population.