The three individuals are two high-ranking government officials and a rebel leader, according to the US Treasury Department. They were targeted for fomenting violence and human rights abuses in the Darfur region of western Sudan, the agency said.

"For too long the people of Darfur have suffered at the hands of a government that is complicit in the bombing, murder and rape of innocent civilians," President Bush said. "My administration has called these actions by their rightful name, genocide. The world has a responsibility to help put an end to it."

Sudan's ambassador to the United States, John Ukec Lueth, said the problem is not with the Sudanese government, but with the rebels who have refused to sign the May 2006 Darfur peace agreement.

Despite the pact, which was backed by the United States and other western nations, fighting among the government of Sudan, the Janjaweed militia and splintered rebel groups has continued unabated.

Deputy Secretary of State John Negroponte said that the Sudanese government continues to block the deployment of a 23,000-strong UN and African Union peacekeeping force for Darfur and obstruct the flow of international aid to the region. There is a poorly equipped contingent of some 7,000 African Union troops in Darfur.

Fighting between government-backed militias and rebel groups in Darfur has killed more than 200,000 people around driven about 2 million from their homes.