Fears are mounting at the World Summit in Johannesburg that stark differences of opinion between rich and poor nations will prevent delegates from approving a draft document before heads of state arrive next week.

This just isn't good enough

Hans Christian Schmidt Danish Environment Minister

While the bulk of a text has been agreed, a string of key issues remain unresolved, from targets on cleaning up energy supplies, being resisted by the Americans, to cuts in Western farm subsidies, as urged by developing countries.

Several campaign groups, including Greenpeace and Oxfam, have pulled out of negotiations, saying that agreements reached on aspects of trade and globalisation were watered down to such an extent they were practically worthless.

"What we fear is that the World Trade Organisation agenda seems to be overriding the objectives of sustainable development," said Meena Raman of Third World Network.

Diplomatic discussions will take place on Saturday against a backdrop of two massive protest marches to highlight the grievances of some of South Africa's poorest inhabitants.

Key topics

Talks will continue through the weekend and some representatives believe that if the final plan of action is not agreed by 4 September, when the summit is due to end, discussions could drag on for several more days.

Keen to avert a deadlock, South Africa - the summit host - has put forward a list of seven topics it says delegates should now focus on.

• production and consumption
• renewable energy
• sanitation
• biodiversity
• targets and timetables
• access to energy
• natural resources

US intransigence is being seen by European countries as a key problem of the summit.

Washington is refusing to contemplate binding targets for introducing renewable energy technologies like wind and solar power, which do not pollute the planet.

The EU wants a target of 15%.

Greenpeace has accused the US and Japan of horse-trading behind close doors. Washington's delegates, it alleged, were offering to promote access to clean water in exchange for Japan supporting a removal of renewable energy targets.

On trade, countries have agreed a text that recognises "the major role trade can play in achieving sustainable development and in alleviating poverty".

The EU's energy targets find no favour with the US

But delegates are stuck on subsidies and tariffs issues affecting the movement of goods from the developing world onto the markets of the richer nations.

Some delegates doubt that a text will be approved by the time heads of state arrive.

"The 100-or-so first ministers who will be assembling will want to know what their environment ministers have been doing," said Canadian delegate David Anderson.

The European Union, meanwhile, warned in a statement that a "sense of urgency is required".

Readying to rally

Thousands of protesters are preparing to descend on the summit to demonstrate against globalisation.

The march, which is due to attract a range of activists - from debt reduction campaigners to pro-Palestinian lobbyists, will start in the slum shanty township of Alexandra and proceed to the conference centre in the wealthy suburb of Sandton.

South African President Thabo Mbeki will address the protesters before they start their nine kilometre (six mile) march.

Justice Minister Penuell Maduna has already warned that the kind of violence which has erupted at other international summits will not be tolerated.

"We won't allow the spirit of Seattle and Genoa to visit us," he said. "We will not allow a disruption of the lives of ordinary people."