When Barack Obama won the US presidential election last year, one of the first papers prepared for him was a sober and prescient document drafted by the National Intelligence Council in Washington.

It was a forecast of how the world would look in 2025, and it did not pull any punches. It predicted a fundamental shift in relative wealth and economic power from west to east, and an abrupt end to the “unipolar moment” the US had enjoyed since the end of the cold war in 1989. The world was in for a bumpy ride, it said, with competition for ever scarcer resources and a gradual transition to a new global power balance.

One of the more mischievous scenarios dreamt up by the intelligence analysts was entitled “A World Without the West”. It took the form of an imaginary letter from the head of the Shanghai Co-operation Organisation to the secretary-general of Nato, dated June 15 2015. It explained how the SCO – an odd assortment of China and Russia, plus several central Asian states – had caught up, indeed overtaken, the Atlantic alliance in military power and international importance.

That letter may well be in the back of Mr Obama's mind as he agonises over how to stabilise the situation in Afghanistan and secure a dignified exit for the US-led Nato forces struggling to cope with the Taliban insurgency. It suggests that the decline of the west began precisely when Nato “pulled out of Afghanistan without accomplishing [its] mission of pacifying the Taliban”. That, combined with an outbreak of trade protectionism in both the US and the European Union, is supposed to have led Beijing to throw in its lot with Moscow and turn the organisation into a military alliance.

The SCO, of course, is for real, although the letter is not. The question is whether it will become a really serious player or is merely a temporary alliance of convenience.

To judge by its latest meeting in Beijing this week, chaired by Wen Jiabao, the Chinese premier, and attended by Russia's Vladimir Putin and four other prime ministers, it is a dog that does not bark. Although advance briefings suggested that the Council of Heads of Government would discuss not only joint efforts to tackle the global economic crisis but also counter-terrorism and Afghanistan, their lengthy communiqué referred only to matters of economic and commercial co-operation.

Yet pure logic suggests that the SCO could and should be doing much more to promote a stable solution in Afghanistan – and that Nato should be doing more to engage it.

The Shanghai members, including Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan, with India, Iran, Mongolia and Pakistan as observers, share a powerful interest in combating terrorism and Islamist fundamentalism. Its members are also concerned to curb drug trafficking. Afghanistan in turmoil is an obvious source of both.

Disturbances in China's north-west province of Xinjiang, bordering virtually every country in the region (including a tiny corner of Afghanistan), have made Beijing extremely nervous about the rise of Muslim militancy among the minority Uighurs.

Communications between Nato and the SCO, however, are minimal.

Part of the problem is that the SCO masks very different ambitions between Russia and China. Moscow is clearly keen to use it to provide a counterweight to US influence in the region and assert Russian leadership in questions of energy supply – not least to China. Beijing sees it as a way of extending its own influence in former Soviet central Asia. It is an alliance of convenience, not trust. America matters far more to China than Russia does.

Moscow is torn between wanting Nato to fail in Afghanistan, and not wanting to see a return to the Taliban. China is already investing there, but is not inclined to take sides: heavy border security is its strategy.

None of the SCO wants to get directly embroiled in the Nato conflict. They fear the intervention stokes terrorism, rather than defeating it.

In Brussels there is a growing lobby for engagement and a feeling that the SCO might be the right place to find it. It could include extending supply routes, training and equipment for Afghan security forces, anti- narcotics training and, intelligence co-operation.

The thinking at Nato is that it would provide the forum for a security discussion with China, as well as Russia, instead of leaving them semi- detached. But nobody seems ready to make the first move. Perhaps they are afraid the imaginary letter will come true.