The most eagerly-anticipated night of the Olympic Games in China will feature the head-to-head duel between Liu Xiang, a national icon and Beckham-esque megastar, and Dayron Robles, a bespectacled Cuban who has recently wrestled the 100m hurdles world record from his rival.

China loves Liu with a passion. He is revered not only for being an Olympic champion, but for being one in a power-and-speed event, thus debunking an ingrained racial stereotype. The final on August 21 is for many Chinese the moment of reckoning when they can declare whether or not the Games have been a success. "It's a kind of miracle and I will work more miracles in the future," Liu said after his triumph in Athens.

The lines are clearly drawn, but Robles has added more fire to the rivalry by being one of 40 athletes to put his name to an open letter condemning China's human rights record. Blanka Vlasic, the world champion at the high jump, is also a signatory to the Amnesty International letter, but it is Robles' name that is most significant.

The letter to Hu Jinato, China's president, demands an end to the death penalty and a guarantee "that human rights defenders are no longer intimidated or imprisoned." Few track athletes have previously contributed to the human rights' issue, but 40 names were gathered at a Golden League meeting in Berlin this summer and Robles' involvement will heighten expectation on Liu's shoulders.

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Robles, 21, is a colourful figure. He likes to party and is the son of Gualberto, a musician who passed away in 1998 and his inspiration. His uncle, Eulogio, was a member of the Cuban national team in the 1970s at the 400m hurdles, while his mother, Regla Mercy, was a keen volleyball player. "I train every day to become the best athlete in the world so I don’t fear anyone," he said, "including Xiang."

The importance of Liu to China cannot be overestimated. Charlie Denson, the Nike brand president, said: "When I think of Liu I think of Michael Johnson in the mid-Eighties and I think of Tiger Woods." He is forced to live a monastic life away from the cloying grasp of his public and gives 25 per cent of his commercial earnings to the national and provincial athletic federations.

Feng Shuyong, head coach of the Chinese athletics team, explained his popularity with an admission that hinted at a widespread insecurity. "Chinese people are not as good as Europeans and Americans," he said. "You cannot easily find youngsters with the right body shape. Yet if I go to Europe or America they are everywhere. Liu's success has shown us something - there are 1.3 billion people here so for sure there are some others out there like him."