Nearly 40,000 people are expected to attend the summit, which will focus on how to make the best use of the Earth's natural resources.

Some critics say the organisers have given too much ground to the corporate agenda, and protests against the heavy business presence are expected later in the week.

However Ian Johnson, the World Bank's vice-president for sustainable development, has defended their presence. "If they hadn't turned up there would be equal criticism," he said.

"They are here because many of them believe in what is called the triple bottom line - making profits, but doing so in an environmentally and socially responsible manner," he told the BBC's World Business Report.

The business presence can in part be seen as an acceptance of the role that business must play if the summit's aims are to be reached.

Issues on the agenda include pollution and global warming.

"Climate change and the evidence that the climate is changing is now very strong, and evidence that energy use and particularly carbon energy use has been the cause of that is very strong," Nick Stern, chief economist of the World Bank, told the BBC's World Business Report.

"The challenge is to set out the evidence about what's happening, what the causes are, and to try to get people to understand those causes and... recognise the responsibilities, not only to themselves and their own countries but responsibilities globally," he added.

Scattered venues

Critics of the summit question how environmentally friendly it is to have 40,000 people suddenly arriving in Africa, driving to conference venues scattered around Johannesburg.

Daimler Chrysler is supplying a thousand cars, vans and coaches to the conference in return for a credit as a sponsor.

But Dr R H Reider of Daimler Chrysler said big car companies are trying to take steps towards sustainable development by developing cars which don't necessarily rely on fossil fuel.

"Daimler Chrysler will, as far as I know, be introducing in 2003 prototype buses and coaches that are based on fuel cell propulsion," he said.

"In 2004 we will have the first passenger car with a fuel cell engine. And we think in probably 2009/2010 that we will have a longer high volume run of fuel cell powered passenger car vehicles."