America's biggest media organisations are engaged in a massive expedition to Beijing to provide round-the-clock coverage of the Summer Olympics, and they promise a truly Olympian affair.

Thousands of journalists, producers, presenters, runners, technicians and gofers are being shipped out from the US to giant media cities-within-cities to bring the folks back home a view of the games the likes of which they have never seen.

But China has strict rules governing journalists' movements and the topics about which they report, so if any member of this media legion decides to stray too far outside of the realms of simple sports coverage, they may get more - or rather less - than they bargained for.

NBC Universal, owner of the NBC TV Network, is America's official Olympics broadcaster and is sending the biggest contingent to the games. It paid $894m (£449m) for the exclusive rights to broadcast 3,600 hours of coverage.

The deal with the International Olympic Committee was part of a record-breaking $2.3bn package to give NBC the exclusive US media rights to the 2004 Summer Olympics ($793m), the 2006 Winter Games ($613m) and the 2008 Summer Olympics in Beijing. The network has since paid a further $2bn for the exclusive US media rights to cover the 2010 Winter Games ($820m) and the 2012 Olympics in London ($1.18bn).

NBC promises to broadcast around the clock, using TV, internet and mobile phone technology to give viewers 'three-screen' access to the games for the first time. Of the 3,600 hours of coverage, more than 2,900 will be live - more than all the live US coverage of all prior televised Summer Olympics.

With two weeks to go until the games begin, NBC has already sold about $900m of its $1bn advertising target, while its parent GE has spent many millions more as one of the top-tier official sponsors.

NBC - as official US broadcaster - has had a relatively hassle-free time in China but a common series of complaints is emerging among those who work for non-rights-owning organisations.

Vital equipment is being delayed at customs. Access to politically sensitive venues like Tiananmen Square is being restricted, despite assurances from the government that such obstructions would be lifted for the Olympics. Even something as simple as parking a satellite broadcast truck on the street is proving almost impossible for many outlets, while in the smaller cities officials have been actively hostile to journalists.

China has tried to give the impression that it has relaxed many of its despotic media restrictions for the Olympics. It was with great fanfare that a new set of rules for foreign journalists was established more than 18 months ago. The rules sought to lift the requirement for journalists to apply to officialdom when they wanted to travel or set up an interview. Even though the harsh rules were rarely enforced, lifting them was seen as a leap forward.

But little has changed, according to Anthony Kuhn, a veteran reporter on China for America's National Public Radio. 'I was arrested while reporting a story just weeks after the rules were changed,' he said from his Beijing office. 'I was reporting on farmland being taken away by government in Shanxi province and all of a sudden I was detained and told I was trespassing in a military zone, which was not the case.'

Kuhn has been arrested on similarly trumped-up charges six or seven times since the rules were supposedly relaxed in December 2007. 'The Chinese government makes all the right noises and promises to modernise things for foreign media but in practice the new rules are almost unenforceable when you get out in the provinces,' he says.

CNN, which boasts one of the longest-standing Western media presences in Beijing, has tried to sidestep many of the problems its competitors face by teaming up with BMC, an arm of the official Beijing TV company. But still, the network has hit serious impediments.

'We faced daunting political and logistic hurdles preparing for the coverage of the Beijing Olympics,' says Jaime FlorCruz, CNN's Beijing bureau chief. 'We still face frequent push-backs. Some of our requests for interviews and shoots are turned down. Logistics have been difficult too, but after some hiccups they seem to have fallen into place.'

China promised back in 2001 that 'there will be no restrictions on journalists reporting on the Olympic Games'. But it is clear this is not the case.

'I have spoken to journalists who say they have been denied press credentials to cover the Olympics because they have spoken or written about China's human rights record, and issues like Darfur or Tibet,' says Richard Bush, director of the Center for Northeast Asian Policy Studies and a fellow of the Brookings Institution, a Washington DC think-tank.

Indeed, reports also suggest that the government has ramped up visa restrictions and has clamped down on allowances for protests in and around Olympic events after the turmoil that surrounded the Olympic torch relay earlier this year.

Internet censorship has also been addressed, in part, for the duration of the games, as foreigners will be able to access much of what is available to them outside China but only from their designated internet access points in the various media locations and their hotels.

'The real question,' Kuhn says, 'is how many restrictions Chinese journalists face, and what kind of internet censorship ordinary Chinese have to put up with?'

It must not be forgotten, though, that China invited a media operation of a previously unimagined scale into the country, and is trying to meet its demands. And the regime is trying to balance the needs of journalists with the real threat of a security breach. In Beijing, model plane flights have been banned for the duration of the games, while unessential medical operations have been stopped to make sure there is an adequate supply of blood in case of a terrorist attack.

'Hopefully foreign journalists visiting China for the first time will take the time to look beyond the propaganda,' says Kuhn, adding that he believes the games have brought a modicum of hope to those wanting media reform.

'The fact is that the rules for foreign journalists have been changed. And I think to some extent you can't put the genie back in the bottle.'