Mahmoud Ahmadinejad made the offer at a summit of the Shanghai Co-operation Organisation (SCO) on Thursday.

He was attending as one of four observer states, but his presence threatened to overshadow the meeting, upstage his hosts and irritate the United States.

"Iran is ready to further expand co-operation with SCO member states in the interest of international peace and security," Ahmadinejad said in a speech broadcast on Chinese television.

He was speaking after leaders of the SCO's six members, China, Russia, Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan, had assembled for the one-day summit in China's financial capital, hoping to tighten security co-operation.

He said Iran, the world's fourth-largest oil producer, was ready to host a meeting of energy ministers from SCO countries to explore more effective co-operation in the exploration, exploitation, transport and processing of oil and gas.

Iran is China's third-biggest supplier of crude oil imports.

The SCO was set up out of the "Shanghai Five" which was founded in 1996 to demilitarise the border between China and the former Soviet Union.

US opposition

Iran's inclusion in the group - albeit as an observer along with India, Pakistan and Mongolia - has particularly angered the US.

Donald Rumsfeld, the US defence secretary, said: "It strikes me as passing strange that one would want to bring into an organisation that says it's against terrorism one of the nations that's the leading terrorist nation in the world."

But leaders of China, Russia and Central Asia defended the participation of Iran, saying that the group served as a force for stability and not as an emerging anti-US bloc.

The group leaders did not directly address Tehran's standoff with the West over Iran's nuclear programme. But they defended the SCO's embrace of Iran as positive for regional stability.