WASHINGTON — President al-Bashir of Sudan must halt military operations in Darfur and “unconditionally” accept a U.N. force or face international punishment if he chooses “confrontation,” Secretary of State Rice said yesterday.

If Sudan “continues waging war against its own citizens, challenging the African Union, undermining its peacekeeping force, and threatening the international community, then the regime in Khartoum will be held responsible, and it alone will bear the consequences,” Ms. Rice told the Africa Society in Washington.

Sudan’s ambassador to the United Nations, Abdalmahmood Abdalhaleem Mohamad, said after Ms. Rice’s speech that “the language of warning and pressure” won’t work on his government. In an interview with CNN, he also accused the American government of inflating the death toll in Darfur to justify its assertion that the violence amounts to genocide.

Ms. Rice’s message on Sudan came as America is ramping up its attention to the Darfur issue, which had eased since the departure of Robert Zoellick as deputy secretary of state. Mr. Zoellick negotiated a fragile Darfur peace accord in May. The State Department’s chief Sudan mediator, Roger Winter, left in August.

Last week, President Bush appointed a presidential envoy to Sudan, former foreign-aid chief Andrew Natsios, and Ms. Rice held meetings on Sudan during the U.N. General Assembly. Yesterday, she announced the appointment of Mr. Bush’s senior Africa adviser at the White House, Cindy Courville, as the first American ambassador to the Addis Ababa, Ethiopia-based African Union.

With 7,200 troops and limited resources, the African Union has been unable to provide peace and security to the people of Darfur, caught in a battle between government militias and rebels. Its difficulties triggered the international effort to transform that force into a 20,000-person U.N. mission.

Appointing an ambassador to the A.U. is designed to “raise” the organization’s profile and “recognize its importance,” Ms. Courville said after Ms. Rice’s speech.

The American effort to deploy U.N. peacekeepers in an attempt to halt rapes, executions, and the destruction of communities in Darfur has faltered due to Chinese and Russian resistance and Mr. Bashir’s opposition.

Ms. Rice said China, with extensive investments in Sudan’s growing oil industry, has “substantial” leverage over Sudan, and she urged Chinese officials to support U.N. resolutions censuring Sudan, rather than to abstain. China holds one of five permanent seats on the Security Council.

While Ms. Rice spoke of “consequences for Sudan,” the most recent U.N. Security Council resolution passed in August outlines no potential sanctions for the Sudanese government for refusing to permit a U.N. force in Darfur, and no one has raised the prospect of military action.