Secretary of State Colin Powell will travel to western Sudan next week for a first-hand look at the humanitarian crisis that has left more than 1 million persons displaced

State Department spokesman Richard Boucher said Powell will meet with relief workers and victims of the crisis in Darfur province.

Powell will make the visit after accompanying President Bush to a NATO summit meeting in Istanbul, Turkey. It is a rare visit - Sudan was last visited by a U.S. secretary of state when Cyrus Vance stopped in Khartoum in 1978 on a trip to Africa.

The Bush administration has said that government-backed Arab militias are primarily responsible for the situation in Darfur, described by many experts as the world's worst humanitarian crisis.

Sudanese President Omar el-Bashir said last week that he would take steps to disarm the militias, but Boucher said little progress has been made toward that objective.

The United States has sent more than a dozen humanitarian flights to Darfur but has said that government restrictions have limited the ability of donor countries to meet the needs of victims.

"There is an extreme urgency," Boucher said. He said a "cleansing" process was under way, with African villages uprooted by militia and African villages nearby left untouched.

The spokesman, citing Sudan's cooperation in countering terrorism, said U.S. relations with Sudan were good.