The U.N. Security Council has refused to hear a briefing on Darfur from the world body's top expert on genocide. The United States angered some Council members by joining a move to block the briefing.

The 15-member Security Council Monday heard a presentation on Darfur from Assistant Secretary General for Peacekeeping Hedi Annabi. But in a closed session, ambassadors declined to hear a separate briefing by Secretary-General Kofi Annan's special adviser on prevention of genocide, Juan Mendez. Mr. Mendez visited Darfur late last month.

Instead, the Council received Mr. Mendez's written report, which tells of escalating banditry and attacks by pro-government Arab militia known as Janjaweed.

Secretary-General Annan, backed by European ambassadors, had asked that Mr. Mendez brief the Council. But the United States, joined by Sudan's allies on the Council China, Russia and Algeria, blocked the request.

U.S. Ambassador John Bolton told reporters afterward that Washington favors strong action to halt the violence in Darfur, but objected to the briefing on procedural grounds.

"One question is, how many officials from the secretariat does it take to give a briefing, and the assistant secretary-general was there, he could give the briefing and that's one way to get it, another way is to get it in writing," Mr. Bolton. "But my question is why are we talking about points of process. Why isn't the Council talking more about steps it could take to do something about the deteriorating security situation? That's what the council should be talking about."

The Council's refusal to hear Mr. Mendez's briefing angered several member countries. France's U.N. Ambassador Jean Marc de La Sabliere took the unusual step of issuing a statement saying he both regretted and deplored the decision. The statement said "it is a matter of principle that the special representative of the secretary-general be heard when the secretary-general deems it necessary."

At a hastily arranged news conference after the meeting, Mr. Mendez said he had found conditions in Darfur last month more dangerous and worrisome than he had expected. He spoke of a "great state of lawlessness" all over West Darfur, and said attacks on camps of IDPs, or internally displaced persons, by Janjaweed militias, are in some ways worse than at the height of the most severe outbreak of violence two years ago.

"But until last week there had never concerted, massive attacks of an indiscriminate nature against civilians in camps," Mr. Mendez. "And now there have been two in successive days. One in West Darfur, and one in North Darfur, and in one of them, the attackers went in on horseback, and the other one apparently in trucks of the Sudanese army, just like it happened in villages in 2003-2004."

Mr. Mendez said Sudanese officials are taking only superficial steps to prevent Janjaweed attacks and human rights abuses that the United States has labeled genocide.

"There hasn't been any disarmament of the Janjaweed, and there hasn't been even a plan to disarm the Janjaweed. In fact, no one talks about the Janjaweed any more, and whether they can be called something or other? I don't have any doubt in my mind that a fighting force that constitutes a militia that's very highly organized and that has ties to the government of Sudan is still very much in operation," Mr. Mendez.

Mr. Mendez urged that those responsible be brought before the International Criminal Court at The Hague. The United States opposes the international court on the grounds that it could be used for frivolous or politically motivated prosecutions of U.S. citizens.

Ambassador Bolton Monday said the United States wants the Security Council to consider whether existing sanctions against Sudan are working, or whether in his words, "there are other steps that could be taken, steps other than talking."