The recurring diplomatic dilemma between dialogue and ostracism, between hope and despair, has returned once again - this time over China and its involvement in Darfur.

The attitude of the Chinese Government is the key to whether the Sudanese Government can be influenced to change its policies and help to stop the killing in Darfur.

China's rapid emergence on the world stage has been partly due to its willingness to invest and prospect where others fear to tread. Chinese companies can often be found operating in and sometimes bolstering the economies of what other countries describe as pariah states. For some time, criticism, ostracism and even the threat of sanctions had no effect.

But now China seems increasingly aware of the risks of doing business with bad politicians and pariah states. There has been a definite change of tone and China has changed its position on the Security Council resolution last summer, which allowed for the deployment of a joint UN and African Union mission to the region. This reversal would never have happened without private negotiations with the Sudanese.

For politicians and activists who have long been calling for peace in Darfur, this breakthrough has been bittersweet. On the one hand, it means the deployment of an effective peacekeeping force could be imminent; an answer to the pleas of all of us around the world.

But on the other, it serves to prove how much more could be done worldwide with more help from China. Beijing is the most powerful voice as far as Khartoum is concerned. If it will weigh in more decisively, the lives of millions of displaced families in Darfur could be transformed.

In the past couple of weeks, there have been more grounds for cautious optimism, with a senior Chinese diplomat actually issuing a public warning to Sudanese politicians that the world was “running out of patience on Darfur”.

The organisers of the Olympic Games this summer are only too aware of the rising disillusionment over China's failure to be part of the solution to this appalling crisis. The energy of the world's youth is being marshalled to protest.

Tomorrow morning London hosts a torch-lighting ceremony to commemorate victims of mass atrocities and to highlight China's potential role in Darfur. The politicians and Darfuris taking part in a protest outside the Chinese Embassy know, as does the Chinese Government, that it is time for China to embody the spirit of internationalism encapsulated by the Games and exert real influence.

If this is done, dialogue will have proven its worth and the world may well become a more peaceful place.

Lord Owen was Foreign Secretary 1977-79.

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