A State Department delegation due to arrive in South Africa on Thursday will lobby to eliminate offensive provisions about Israel from documents that will be taken up at a U.N. conference on racism.

State Department spokesman Richard Boucher said the degree to which the effort succeeds will determine U.S. representation at the conference, which starts Friday in Durban.

The administration announced Monday that Secretary of State Colin Powell would not attend the conference because of concerns over Arab-backed provisions accusing Israel of engaging in racist practices against Palestinians.

The U.S. delegation, which planned to leave for South Africa Wednesday night, is headed by Michael Southwick, a deputy assistant secretary in the Bureau of International Organizations.

Southwick was in New York working on an upcoming U.N. conference on children when he got the call to head to Durban.

The reluctance of the Bush administration to send a high-level delegation to Durban has added to tensions between the U.S. and the United Nations.

The White House expressed concern Tuesday that the U.N. children's summit next month will proclaim support for abortion counseling and services in its final declaration.

But Boucher insisted the dispute was a normal part of preparation for any U.N. conference.

"We have every expectation that we can work them out, and that we can be there, and that we will be there at a high level," he said. A Cabinet member will likely lead the delegation, he added.

The battles over the racism conference and the session on children is the latest sign of a strained U.S.-U.N. relationship and comes just weeks before President Bush makes his first address to the U.N. General Assembly.

It also follows criticism voiced by several nations over Bush's decision to withhold support for various international treaties. Many also have expressed concern that Bush is moving the United States toward unilateralism.

Richard Falk, an international law professor at Princeton University, said the trend started during the Clinton administration.

"In recent years, both parties, both leaderships have at the same time tried to dominate the U.N. and weaken it as an organization," Falk said. "That's the unfortunate failure for American leadership in the post-Cold War era, and Bush just continues that attitude, perhaps deepens it a bit."

Since taking office, Bush has rejected the Kyoto climate-change treaty, pushed forward with plans for a missile-defense shield and abandoned talks on enforcing a 1972 treaty against germ warfare. The administration also opposes other treaties, including one to create an international criminal court, the world's first permanent war crimes tribunal.

Some believe that it makes sense for the administration to avoid U.N. conferences it opposes -- as long as it provides alternatives.

"If you're bailing out of everything, it reduces the political value of bailing out of things in particular," said Timothy Crawford, a postdoctoral fellow at the Brookings Institution's Foreign Policy Studies.

A key source of U.S.-U.N. tension has been Congress, which is linking the payment of $463 million in back dues to a stipulation barring U.S. funding of the international court.

Many lawmakers, mostly those in the House, are still angry over the loss earlier this year of U.S. seats on two prominent U.N. committees -- a human-rights panel and an anti-drug body.

Bush will address the U.N. General Assembly in New York on Sept. 24, as presidents traditionally do, and the administration expects Congress to pay its U.N. arrears by then. Officials say they are "working intensively with concerned parties on the Hill on the issue."

Others are not so sure. More than eight months after the United States reached a deal with the United Nations to pay part of its debt, "No check has been put in the mail," said U.N. spokesman Fred Eckhard.

Earlier this month, Eckhard said U.N. Secretary-General Kofi Annan noted that "for a country in the U.S.'s position, this failure to pay undermines its leadership and its effectiveness in the U.N."

Despite the resentment, the United Nations will continue to seek American input, Falk said.

"There's a broad recognition that despite the criticism of the United States, the U.S. is a necessary participant in any kind of effective U.N. undertaking," Falk said.