ADDIS ABABA, July 8, 2005 (AP) -- The African Union will begin reinforcing its peacekeeping force in Sudan's western Darfur region on Saturday, but the organization faces a US$200 million (A€167 million) funding shortage for the operation, an official said Friday.

The 53-nation organization has around 3,200 peacekeepers and civilian police officers in Darfur, but will more than double the size of force by the end of September, said AU's Peace and Security Commissioner Said Djinnit.

Some 680 Nigerian reinforcements are set to deploy to Darfur on Saturday as part of an expanded force of 7,170 peacekeepers. Additional soldiers will fly in before July 15 _ regardless of the cash shortage, Djinnit said.

"Our partners should realize we have a financial gap" in efforts to stabilize Darfur, that has been described as the scene of one of the world's worst humanitarian crises, Djinnit told journalists at the AU headquarters in Ethiopia's capital, Addis Ababa.

"We have a shortfall of around US$200 million (A€167 million) as of today. It is a source of concern," he said.

Rebels from black African tribes took up arms in Darfur in February 2003, complaining of discrimination and oppression by Sudan's Arab-dominated government. The government is accused of responding by backing a counterinsurgency by Arab militia known as the Janjaweed.

War-induced hunger and disease have killed more than 180,000 people and driven more than 2 million from their homes, according to U.N. estimates.

The African Union is trying to secure cash from Canada and part of European Union's A€250 million (US$299 million) peace fund set up last year.

Djinnit praised this week's signing of a declaration of principles between the government and Darfur rebels for negotiating an end to the conflict.