Michael Phelps and Liu Xiang hope to grace superb venues with sports heroics at the Beijing Olympics against a backdrop of politics and pollution.

The first games in the world's most populous country has politics written all over it as concerns around China's human rights record reached new heights after its dealing with the unrest in Tibet.

An earthquake in the Sichuan province, Beijing's notorious pollution and algae at the sailing venue also made headlines instead of sport in the final countdown to the Aug 8-24 Games.

That was bad news for the Chinese who want the headlines to focus on top class sport in state-of-the-art arenas when 10,500 athletes from more than 200 countries compete for 302 gold medals in 28 sports.

The International Olympic Committee (IOC) will try to ensure a clean competition with a record 4,500 doping tests.

'Bringing Olympic values to one-fifth of the world's population is arguably one of the most exciting projects in Olympic history,' IOC president Jacques Rogge once said.

The American swimmer Phelps is out to better the seven gold medals compatriot Mark Spitz won at one Olympics, in 1972. Phelps already has six golds and needs just four more from his eight events to achieve an historic 10 golds overall at the Olympics.

But Phelps has shrugged off the issue, saying 'I don't talk about it. I just go into the water and compete.'

While Phelps should go unrivalled in the Water Cube, a superb duel may emerge in the blue-riband 100 metres sprint in the adjacent national stadium at the athletics competition.

World champion Tyson Gay aims to continue a proud US tradition with the gold, but is up against Usain Bolt (the world record holder) and Asafa Powell (the former world record holder), who want Jamaica's first ever 100m gold.

China's hopes rest on the 110m hurdler Liu, who has gold from the 2004 Olympics and 2007 worlds. But he also has a formidable challenger in Cuban Dayron Robles, who recently stole the world record from Liu.

The big Chinese team gave an ominous warning of its strength in Athens as part of an 'Asian awakening' and there is speculation whether the home team can topple the US, which garnered 102 medals in 2004 (36 gold, 39 silver and 27 bronze).

Others at the centre of attention include a host of basketball stars ranging from Kobe Bryant to China's Yao Ming, world number one tennis player Roger Federer and his rival Rafael Nadal, as well as footballers such as Lionel Messi and Ronaldinho.

Not present, by contrast, over doping infringements are among others the entire Bulgarian weightlifting team and Justin Gatlin, the 100m gold medallist from 2004.

The IOC aims to make sure with 4,500 drug tests (up from 3,600 in 2004) that the Beijing competition is clean. In addition, athletes caught are automatically barred from competing 2012 in London.

'Most athletes compete honestly and fairly. They treasure the Olympic experience. We owe it to these athletes - who train so hard - to ensure the games are as free of prohibited drugs as possible,' said Rogge.

It remains open how athletes will express their views on political issues such as Tibet, and how free the 25,000 media will be in their reporting.

China has guaranteed freedom of press, for the foreign media during the games, and also no internet restrictions which are normally imposed by the Communist government.

'I believe the games will definitely bring something to China, and definitely an openness to the country which is unprecedented. I think the Chinese will know much more about the world than they know today and the world much more about China,' Rogge told DPA in mid-July.

Shao Shiwei from the organising committee media department struck a similar line earlier this year: 'The Olympics help to bring China in line with the rest of the world, to make it more open to the world.'

But the political issues could overshadow sport, which would be a blow for China in its aim to showcase the country through the Games.

According to the New York Times, 'China has spent eight years and tens of billions of dollars preparing to host the summer games, which Beijing has envisioned as a kind of coming-of-age party to showcase its rapid growth.'

The Chinese have virtually left no stone unturned, erected venues in record times, moved entire factories to ease the grave pollution problem, have a big-brother-like eye on every aspect of food safety and will use modern technology to make sure it doesn't rain during the ceremonies.

The government did not declare a total budget, saying only that the operational costs of the Games would not exceed the $2.4 billion spent by Athens in 2004.

But with environmental efforts alone of around $12 billion, a new airport terminal and several new subway lines built in a major city infrastructure overhaul, the overall figure should be several tens of billions of dollars.