Negotiations to finalize the agreement to be adopted by heads of state and government at the World Summit on Sustainable Development are continuing at a frenzied pace as world leaders arrive in Johannesburg.

A continuous stream of aircraft carrying more than 100 heads of state and government to the earth summit are arriving at Johannesburg international airport. Across town, government ministers are working night and day to finalize the agreement their leaders are scheduled to adopt Thursday at the end of the summit.

But several important issues remain outstanding. Among them are: targeted deadlines on reducing by half the number of people in the developing world who lack clean water and sanitation, switching to renewable energy sources, and good governance. And some countries and non-government delegations are asking whether the focus on partnership agreements at the summit has overtaken the importance of setting targets.

Paul Nielson, the European Union Commissioner for Development and Humanitarian Health says that both approaches are needed, and he sees no conflict between them.

"We do see that we need a strong inter-governmental level of commitment on what targets to achieve by 2010, 2015, 2020 as we have discussed in these negotiations over the past week or so," he said. "But at the same time, and without diluting in any way the commitment undertaken by governments, we also need partnerships in order to improve on the implementation that we are taking."

As hosts, members of the South African delegation have been playing a pivotal role in facilitating negotiations, trying to bring opposing views together so that agreements can be reached.

Trade and Industry Minister Alec Erwin told reporters that it would be unwise for anyone to underestimate the importance of the agreements being negotiated for the economies of the countries of the world. Mr. Erwin said it is therefore not surprising that negotiations are proving a challenge.

"We should bear in mind that at most major conferences, certainly in Doha, it took us right to the 11th hour before we concluded what was in the end an historic agreement," he said. "And South Africa's view is that we have a very realistic prospect of getting another equally historic agreement in Johannesburg."

Mr. Erwin says he is not speaking as what he called a cheerful and optimistic South African. Rather he said his view is informed by his strong belief that no country has come to Johannesburg intending to jeopardize the work of the summit.

"I do not think any delegation here can seriously want to jeopardize the serious work that has been done," he said. "Some very, very interesting and important new negotiations are being proposed for bio-diversity and other areas. And I think there is not a single serious delegation here that would want to see that jeopardized in any way."

But those delegates with a less hopeful outlook than Mr. Erwin's warn that unless disagreements on key issues are soon resolved, the many agreements already reached will also be threatened.