U.S. officials say they will use a U.N. summit in South Africa next week as a platform for refuting world criticisms of President Bush's policies on the environment and aiding the world's poor.

Secretary of State Colin Powell will head the U.S. delegation to the summit, which runs Aug. 26 through Sept. 4 in Johannesburg. Powell will be on hand for the last few days of the summit, although other U.S. officials will be there beforehand.

That fact alone drew criticism — that Bush, unlike other heads of state, ignored calls to attend the summit himself because he has adopted a go-it-alone stance toward some global concerns, like climate change.

A senior administration official, speaking to reporters on condition of anonymity, said Wednesday that Powell and other members of the U.S. delegation will highlight $4.5 billion in programs for developing nations and stress public-private partnerships to address needs such as water, ending hunger, preserving Congo Basin forests and providing better access to energy.

They also will take the chance to "address questions that may be out there regarding our record,'' the official said.

Paula Dobriansky, undersecretary of state for global affairs, said the United States expects this summit to pick up where two others — a trade gathering in Doha, Qatar, and a development summit in Monterrey, Mexico — left off. The Johannesburg session is billed as a follow-up to the 1992 Earth Summit in Brazil.

"What we hope is to see a continuum of a process that has started,'' Dobriansky said. "In Johannesburg, we want to see results.''

Bush attended the Monterrey meeting last March and unveiled his plan for requiring countries to make progress on economic and social reform to be eligible for U.S. aid. He also attended the annual summit of industrialized nations in Canada in June, where much of the focus was on helping the most downtrodden nations in Africa.

After leaving South Africa, Powell will go to Angola and Gabon, two of the world's leading oil-producing nations. One official said oil might be discussed, but would not be a focal point of Powell's talks in those countries.

In Angola, Powell plans to visit a camp for Angolans displaced by civil war. In Gabon he will meet with non-governmental organizations on preserving forests.

Powell will meet with various leaders on the sidelines of the summit, one official said, to address Africa's more bedeviling political struggles: a fragile peace arrangement in Congo, land seizures in Zimbabwe and the death-by-stoning sentence given a Nigerian woman by an Islamic court.