Some of the world's most powerful business leaders have been told they must invest in developing countries for the mutual benefit of rich and poor.

The call at the World Development Summit came from United Nations Secretary-General Kofi Annan, who said that sustainable business investment was essential if poor countries were to escape poverty.

"Today there is a growing recognition all around that lasting and effective answers can only be found if business joins in partnership and works with others," he said in Johannesburg.

We're close to the wire, we're on the last lap

Nitin Desai, summit secretary-general

"It is only by mobilising the corporate sector that we can make significant progress."

He said that since the first Earth summit ten years ago, business leaders had realised that if they wanted to survive, in a sometimes hostile global economy, they had to respond to social and environmental challenges.

Business leaders called for more dialogue between companies and environmental campaigners at the summit, challenging the view that they were enemies of the green movement.

Many countries want to set a deadline for improved water supplies

Shell Oil Chairman Phil Watts urged firms not to take bribes and to work in closer partnership with local firms in developing countries.

However the BBC's Tim Hirsch in Johannesburg says there are disagreements as to whether business activity should be left to voluntary controls or regulated by governments at a global level.

Renewable energy

As the summit enters its second week, negotiators are racing against time to achieve workable agreements as heads of state arrive on Monday.

After a marathon session, delegates said they would reconvene later on Monday to try to resolve the one remaining dispute about energy.

Some countries have been pushing for 10% of the world's power to come from renewable sources by 2010.

But not everyone backs that deadline, and there is also debate about exactly how renewable energy should be defined.

I think the United States is allying itself with some strange partners, and doesn't seem to have supported the human rights language

UN High Commissioner for Human Rights Mary Robinson

"We're close to the wire, we're on the last lap," conference Secretary-General Nitin Desai told Reuters news agency late on Sunday night.

"Countries are finding common ground."

BBC correspondents say a major hurdle remains targets on the use of clean energy such as wind and solar power and on the increase of the provision of decent sanitation for the poor.

Greenpeace activist Steve Sawyer said that the issue of poverty had been reduced to a bargaining tool.

"The US and Japan are punishing, threatening and bullying to try to get anybody who wants to do anything about renewable energy to give it up in exchange for the sanitation target," he said.

'Unholy alliances'

On Sunday, the United Nations High Commissioner for Human Rights condemned the US, accusing it of attempting to undermine her position by wanting to exclude references to human rights from the final conference declaration.

"I'm told there are unholy alliances going on," she told the BBC.

"I think the United States is allying itself with some strange partners, and doesn't seem to have supported the human rights language."