WASHINGTON — Secretary of State Colin Powell has virtually ruled out participation in a U.N. conference on racism because of Arab-backed proposals accusing Israel of racist practices against Palestinians, an administration official says.

"It's increasingly clear he won't go," the official, asking not to be identified, said Sunday night.

The official said Powell's absence from the conference, set to start on Friday in Durban, South Africa, is all but decided. It is not clear whether the administration will be represented at a lower level, the official added.

President Bush told a news conference Friday there will be no U.S. representation at the conference so long as delegates "pick on Israel."

"If they use the forum as a way to isolate our friend and strong ally, we will not participate" at any level, Bush said.

Black civil rights activists have pressed Bush to send Powell to the conference.

Israel wants no reference whatsoever to its conflict with Palestinians, calling it a political rather than racial dispute.

Nasser al-Kidwa, the Palestinian representative to the United Nations, made clear Friday that Israel would be singled out for criticism at Durban.

He said he expected the message of the conference to be that racism was unacceptable, "including those manifestations which are coming from Israel. Israel cannot be exempted from that, period.

"We believe Durban will take clear positions in my opinion with regard to all racist practices by the occupying power," al-Kidwa said.

The United States also has objected to attempts by some delegates to demand reparations for slavery as part of the debate in Durban.

But the administration in recent weeks has directed most of its fire at Arab efforts to condemn Israel.

The conference will run from Friday through Sept. 7.