Steven Spielberg has finally decided he does not want to be part of a holocaust stamped "Made in China". It's an overdue decision – but one that could now begin an Olympic chain reaction to save the starved survivors in Darfur.

Many people will react to this news by asking – what does China have to do with an African genocide unfolding thousands of miles away from its mainland anyway? The answer is stark. China pays for the genocide. China arms the genocide. China obstructs all attempts to stop the genocide. Indeed, the genocidal Sudanese dictatorship is so enmeshed with the Chinese Communist dictatorship that it should be rebranded as Chudan – a pooled government with pooled responsibility.

When I stood last summer on the borders of Darfur, the hacked and broken people I met were victims of Chudan. Their catastrophe began in 2004, when the local Muslim population of Darfur finally grew sick of being neglected and ignored by the oil-rich National Islamic Front government in Khartoum. A few rebel groups began to rise up – and Khartoum reacted with deranged violence. They sent the Arab Janjaweed – "men on horseback" – to slay the uppity black population, so they could never shout out again.

Osman Ibrahim was one of the lucky ones. He's my age – 29 – and when we met, he was running for his life with his wife and four children. One morning a month before, Osman had been tending his crops in his village 30 miles away, when he heard the sound every black Darfuri dreads. It was the whirr of the Sudanese military's helicopters, followed by the approaching horses and machine-gun fire of the Janjaweed. "The helicopters bombed my house," Osman said, "and the Janjaweed started to kill everyone in the village."

He gathered his children and ran. If they had stayed, the Human Rights Watch reports suggest, his wife and children would have been gang-raped, and then they would have all been killed. Some 450,000 people like them have died so far, with more than 2.5 million more on the run.

The helicopter that blew up Osman's village, and the AK-47s that were used to slaughter his friends, were provided and paid for by China. Why? One word: oil. Since 1993, China has been scouring the earth for the few fossil fuels not seized and burned by Europe and America, and it found the friendliest pool of petrol in Sudan. They have ploughed $10bn of capital investment into Sudan's oilfields, and they snaffle 60 per cent of Sudan's petrol: more than 400,000 barrels a day.

What does Sudan get in return? Enough cash to pay for the slaughter – but that's only for starters. Since 1996, China has been Sudan's main supplier of weapons. On the international stage, China covers Sudan's back. Since the genocide began, the Chinese have been systematically obstructing any attempts at the UN to protect Darfur's civilians. China's special envoy, Liu Guijin, visited Darfur and declared, "I didn't see a desperate scenario of people dying of hunger." No, he said – he simply saw people "grateful" for China's "contribution".

Then the threats to disrupt the Olympics came – and they began to shift their tone. It was reported that China voted for a UN resolution authorising a force of 22,500 peacekeepers – but this was mere Sino-spin. In reality, they announced they would only vote for the UN resolution provided a clause was added. The UN must "invite the consent" of the genocidal regime in Khartoum before UN troops could be dispatched, they insisted. Khartoum has predictably refused to consent – so the peacekeeping mission seems to have died in its crib.

Yet if China threatened to turn off the tap on Sudan's economy, arms and international support, the dictatorship would almost certainly wind down the genocide rather than face implosion.

So can we make it happen? It's notoriously hard to pressure the Chinese dictatorship. They keep their population almost totally ignorant about Darfur, hidden away behind the Great Firewall of China – so internal anger on this issue is almost non-existent. That's why the Beijing Olympics are remarkably serendipitous, providing a rare pressure-point for the world's worried citizens.

Enter (and exit) Spielberg. He is a hefty international symbol, one the Chinese dictators cannot shrug off. But alone, he is nothing like enough. Luckily, for the Chinese coming-out party to go well, they need the guests to stick to the dress-code and the strict etiquette they lay down. All moral people should refuse to play along – not for symbolism, but because each pint of shame changes China's calculations. We will succeed in stopping the genocide when the Chinese dictatorship is more frightened of having its $50bn party ruined than of losing 400,000 barrels of Sudanese oil a day.

The best people to help us achieve this are our athletes. Before they are sportsmen, they are men. Before they are sportswomen, they are women. They have a responsibility to other men and women who are being raped and butchered, just for being black. If we learned anything from the 20th century, it is that "I was told to say nothing" is the weakest excuse of all.

So let them pledge to unfurl Darfuri flags from their podiums if they win. Let them promise to hold up pictures of burned Darfuri children. Let them talk about Darfur at every Olympic press conference. The Chinese Communists know they cannot black out every image: they will begin to panic.

Obscenely, the British Olympic Association (BOA) has tried to do the Communist Party's work for it. In the past week, it has attempted to ban all Olympic athletes competing under the Union Jack from even mentioning this holocaust, inserting a "gagging clause" about "politically sensitive subjects" into their contracts.

So far, only one outstanding athlete has refused to shut up about Darfur: the badminton player Richard Vaughan. More need to speak out, today. You can ask the chief executives of the BOA why they are trying to stop them at colin.moynihan@boa.org.uk and simon.clegg@boa.org.uk.

We can also pressure the advertisers. The Chinese are raking in tens of billions from European and American corporations desperate to be associated with the Olympics. The human rights group Dream For Darfur approached the major ones – Coca-Cola, Johnson and Johnson, Panasonic, Volkswagen and more – to ask them simply to speak out on Darfur. They refused. The campaigners called the report: "And now – not a word from our sponsors". If China thought they would lose this revenue, they could be panicked even more.

The first genocide of the 21st century is passing into the night, and the trail of blood runs right back to Beijing. The only question now is – do we want to throw an Olympic party slipping and sliding in the slaughter, or do we want to use this moment to protect Osman and his terrorised countrymen?

j.hari@independent.co.uk