KHARTOUM, Sudan, June 29, 2004 (AP) -- Rebels have looted 57 tons of U.N. food aid from a convoy of trucks in Darfur, a Sudanese Cabinet Minister said Tuesday, speaking shortly before U.S. Secretary of State Colin Powell arrived in the country.

"These types of rebel action are the most serious threat to the humanitarian and security situation" in Darfur, said Ibrahim Hamid, the minister of humanitarian affairs.

The minister did not name the rebel group, but he said the food came from the U.N. Food and Agriculture Organization and was being carried in three trucks. He said the rebels hijacked it between Nyala and Dhayen in south Darfur on Tuesday.

A spokesman for the Food and Agriculture Organization could not be reached Tuesday evening in Rome, where the agency is based. A spokesman for the sister organization, the World Food Program, said in Rome it had no information on any such attack.

Aid organizations and rights groups have accused the Sudanese government of impeding access to Darfur and of backing Arab militia that have been waging a campaign of ethnic cleansing against the western province's people of African origin. The government has denied the charges.

The United Nations says Darfur is the world's worst humanitarian crisis at the moment. Thousands have been killed since two rebels groups took up arms for autonomy for Darfur in February 2003. About a million people have been forced to flee their homes, many to temporary shelters in the desert along the Sudan-Chad border.

Secretary of State Powell arrived in Khartoum on Tuesday evening and is scheduled to visit camps for displaced people in Darfur on Wednesday.

U.N. Secretary-General Kofi Annan is scheduled to arrive in Khartoum on Wednesday and is also due to tour camps of homeless people in the western province.

Both Powell and Annan called on the government Tuesday to do more to rein in the militia that are accused of plundering villages and driving people from their homes. Before his arrival, Powell told reporters the situation in Darfur was "horrific" and required prompt action.

President Omar el-Bashir, who met Powell on Tuesday night, said earlier that all reasons for the rebellion in Darfur had been eliminated, and that his government would solve the crisis through dialogue and security arrangements.

Speaking on the 15th anniversary of the military coup that brought him to power, el-Bashir accused unidentified outside parties of seeking to "internationalize" the Darfur problem, according to a report by the Khartoum correspondent of Egypt's semi-official Middle East News Agency.

El-Bashir accused the rebels of violating the April cease-fire agreement, but said his government would continue to respect it.

The rebels have accused pro-government forces of violating the cease- fire.