ADDIS ABABA, Ethiopia - The African Union is sending 300 troops to Sudan's Darfur region, where more than a million black Africans have fled attacks by marauding Arab militias.

The force will be the first foreign troops to intervene in what the United Nations (news - web sites) has described as the world's worst humanitarian crisis. Their mission is to patrol refugee camps and protect unarmed African Union observers also being sent to the region.

Sam Ibok, the AU director of peace and security, said the troops would be quickly deployed but did not give an exact date. He said the force would include soldiers from Nigeria and Rwanda and possibly Tanzania and Botswana.

"We are discussing with the Sudanese government on the deployment of that protection force," Ibok said. "We cannot describe what has happened in Darfur as genocide, but it has the potential of deteriorating or degenerating into something quite serious."

The mission, announced as African leaders gathered in Addis Ababa for the annual AU summit, could be an important test for the 53-nation organization. The African Union was created two years ago in part to resolve conflicts in the region. So far its only joint military deployment has been the peacekeepers it sent to Burundi in 2003.

Nomadic Arab tribes have long been in conflict with their African farming neighbors over Darfur's water and usable land. The tensions exploded into violence when two African rebel groups took up arms against the government in February 2003 over what they regard as unjust treatment by the government in their struggle with Arab countrymen.

The government signed a cease-fire accord with the rebels in April. But Arab militias have continued a violent campaign to drive black African farmers from the vast western region, U.N. officials and human rights workers say.

The rebel Justice and Equality Movement and the Sudan Liberation Army accuse the government of arming the militias. The government denies any involvement, but across the region, refugees describe how Sudanese airplanes and helicopter gunships back the militia attacks.

U.N. Secretary-General Kofi Annan (news - web sites) has said the crisis is "bordering on ethnic cleansing."

As many as 30,000 people have been killed and more than 1 million others have been forced from their homes, most taking shelter in makeshift camps along the border with Chad.

The U.S. Agency for International Development says many are in desperate need of help. Sen. John McCain on Monday urged quick action to prevent further death.

"This is a horrible thing that's going on," the Arizona Republican said on CNBC. "I think that all the sanctions and all the criticism and everything is appropriate but I also think we ought to fund, we the United States of America, should fund a force made up of military from other African countries to go in there and stop this."

During a visit to the region last week, Secretary of State Colin Powell (news - web
sites) won a commitment from Sudan's President Omar el-Bashir to contain the militias and allow human rights monitors into Darfur.

Powell had earlier said that if Sudan refuses to take decisive steps to cut its ties to the Arab militias, Sudan cannot expect to have normal relations with the United States.

Some 150 unarmed African Union monitors are expected to go to Darfur as part of the April cease-fire agreement. A few African Union monitors already are there.

Meanwhile, a top economic adviser to Annan, speaking at a conference on hunger on the eve of the African Union summit, said African nations should ignore their foreign debts.

"The time has come to end this charade. The debts are unaffordable," said Jeffrey Sachs, director of the Earth Institute at Columbia University and special adviser to Annan on global anti-poverty targets. "If they won't cancel the debts I would suggest obstruction; you do it yourselves."