Negotiators say they are close to a final deal on a package of measures to tackle poverty and environmental damage at the World Summit on Sustainable Development in Johannesburg.

As world leaders gather to approve a plan for action, delegates said differences over targets for providing sanitation for the poor had been settled.

It's gone excellently

South African Trade Minister Alec Erwin

However disputes remain over targets for boosting the use of clean forms of energy such as wind and solar power.

After marathon talks, efforts to resolve the issue are to resume later on Monday, with heads of state and government being consulted to try to break the impasse.

The United States and oil-producing countries object to setting goals.

Environmental groups are already saying that the compromises made to reach agreement represent a step backwards for the planet and for the poor.

'Weak document'

Ministers and officials talked well into Sunday night in an attempt to finalise the plan of action of lifting developing countries out of poverty while easing the pressure on natural resources.

South Africa's Trade Minister Alec Erwin told Reuters news agency the discussions, which went on to about 0315 (0115GMT) had gone "excellently" and that there just had not been enough time to continue talking.

Differences over sanitation were resolved by compromise

Organisers had hoped that a complete package would be agreed before political leaders start addressing the summit on Monday morning.

One of the remaining stumbling blocks was resolved when the United States agreed to accept a reduction in targets on the number of people left without access to proper sanitation

However there was resistance from the US and oil-producing states to calls from the European Union for a timetable on increasing the use of renewable energy.

South Africa's Foreign Minister Nkosazana-Dlamini told journalists on Sunday night the draft plan was not going to be a "strong document".

"To be honest, if you are negotiating with the world, you can't get everybody to accept a strong argument," she said.

Negotiators have already agreed a blueprint to combat Aids, dwindling fish stocks and other issues as part of the overriding goal of reducing poverty by 2015.

'Unholy alliances'

On Sunday, there was also criticism of the US from United Nations High Commissioner for Human Rights Mary Robinson, who accused it of attempting to undermine her position by trying 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."

Some of the world's most powerful business leaders heard a call on Sunday from UN Secretary-General Kofi Annan for greater investment in developing countries.

Mr Annan said sustainable business investment was essential if poor countries were to escape poverty.

There is debate over how renewable energy can be defined

"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.

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.