Delegates meeting in South Africa for the World Summit on Sustainable Development are wrangling over the final wording of the agreement that will be signed when the conference ends. One of the most contentious issues is global trade.

The developed world and the developing world disagree on what the final conference document will say about trade. Developing countries are demanding that developed nations open their markets, lower their trade tariffs and reduce their agricultural subsidies. The United States and the European Union, in particular, are reluctant to sign off on anything that might hurt their economies.

Diplomats have been meeting behind closed doors for days, even before the summit started, trying to hammer out a deal. But the issue continues to hold up agreement on the final conference text.

Environmental activists are largely condemning the U.S. and E.U. position as unsustainable. David Waskow of the advocacy group Friends of the Earth says he fears the issue will, in his words, hijack the summit.

"We are very concerned that this is becoming a trade summit, and it's not supposed to be," he said. "It's supposed to be about protecting the environment and about making sure we can develop economically in a way that's sustainable."

Other environmentalist groups echo that concern. Remi Parmentier of Greenpeace condemns the language that the U.S. and the E.U. have proposed for the final document.

"It praises trade so much," he said. "And of course trade has a very important role in sustainable development and in poverty alleviation. But also the limits that are put to trade are very important and are very key instruments for sustainable development and I can think of a number of international treaties that are restricting trade. You cannot promote trade at all costs, because you just destroy the planet!"

Trade is not the only issue holding up agreement on the final text. Rich and poor nations also disagree over whether good governance should be a condition for receiving aid money. And Europe and the United States are at odds over targets and timetables to ease global poverty, something Europe wants and the U.S. does not.

The head of the U.N. Environment Program, Klaus Toepfer, urged delegates to find a compromise.

"We cannot afford to leave this great summit with the feeling that our differences did not allow us to confront these great challenges of our times," he said.

The summit goes into its second day with U.N. and South African officials saying there has been progress toward a solution on the final text. But they will not give details.

More than 100 heads of state and government are expected to attend the summit, most of them arriving at the end of the week. Negotiators hope to have a deal in place in time for them to sign.