Boucher sahd the United has "called upon the Sudanese government to immediately stop its heavy-handed campaign of harassment and intimidation against Medecins sans Frontieres personnel and humanitarian aid groups who are providing essential services to the people of Darfur."

He said aid workers were providing vital medical care and counseling to thousands of women who continued to be attacked and raped in Darfur.

Boucher said several international, nongovernmental organizations have documented human rights violations committed against innocent civilians under the control of the Sudanese government.

Sudanese authorities have charged one Medecins Sans Frontieres worker with spreading false information and detained a second who is the agency's coordinator in Darfur.

The Darfur conflict erupted when rebels in the western region took up arms against what they saw as years of state neglect and discrimination against Sudanese of African origin.

The government is accused of responding with a counterinsurgency campaign in which government-backed Arab militiamen known as Janjaweed committed wide-scale abuses -- including killings, rape and arson -- against the African population.

More than two years of conflict in Darfur has killed at least 180,000 people, many from war-induced hunger.