Well before the sun rose over the city's winding hills Monday, Col. Charles Karamba was wide awake, ready to give his 120 Rwandan army troops an energetic send-off to western Sudan.

They were to be the first troops airlifted to Darfur on U.S. military planes as part of a two-week mission to move African Union peacekeepers quickly into the war-torn region, where 1.5 million people have been driven from their homes and where violence, hunger and disease have killed tens of thousands.

Two C-130 transport planes, sent by the U.S. Air Force from Ramstein Air Base in Germany, stood ready on the rain-soaked tarmac outside the Rwandan capital. Karamba sat by his phone, waiting for the orders to board.

Instead, just after 10 a.m., word came that the Rwandans would not be leaving quite yet. According to diplomats, that was because Nigeria, whose president heads the African Union, had demanded to go first. Although the airlifts from Kigali were planned last week, diplomats said, Nigerian officials wanted their troops to arrive first as a matter of prestige.

"We had more people ready than we had seats," said Karamba, noting that 237 Rwandan troops were trained and ready to go. "But we will wait. When they are ready, we will be there."

Both Nigerian and African Union officials declined to comment on the confusion, saying only that the Nigerians are now scheduled to deploy before the Rwandans, possibly on Thursday. But Rwandan officials suggested that logistical problems had caused the delay.

"There is no food and no tents, and you don't just throw soldiers out into the desert to fend for themselves," said Foreign Minister Charles Murigande.

The Bush administration has called the atrocities in Darfur genocide, but the airlift is the first American military operation aimed at curbing the violence. No Western countries have been willing to send troops to the region.

The African Union last week approved an expansion of its military presence in Darfur, from 300 to 3,000 troops. Despite an uneasy truce, which is being observed by 150 African Union monitors, violence between rebel and government forces continues to unfold, including reports of rapes and killings.

Last week alone, officials said, 200,000 people were driven from their villages. At the same time, two new rebel factions have emerged in Darfur, including one that African Union officials said attacked a government convoy Oct. 6.

The United Nations, which feeds more than 1 million people in western Sudan, said the African Union mission was urgently needed to protect aid routes. Rebel groups as well as the government-backed Arab militia known as the Janjaweed are accused of blocking aid convoys, and two relief workers were killed last week.

The promised increase of African troops is viewed as a test of the willingness and ability of African governments to help solve the region's problems. Rwandan officials have said they are especially eager to help because of their own country's experience with genocide 10 years ago, in which more than 800,000 people were slaughtered.

Diplomats expressed concern that the dispute over who should be airlifted first could delay getting troops on the ground and saving lives in Darfur. Officials have said that without the airlift and other help, it could take up to a year to deploy the troops.

"Obviously this is holding up the mission," said a Western diplomat in Khartoum, the Sudanese capital. The diplomat said it was up to African Union officials to negotiate "who's going to be first."

The latest round of peace talks between rebels and Sudanese officials resumed in Abuja, the Nigerian capital. But U.N. officials worried that the new rebel groups, who are not participating in the talks, could further derail peace efforts.

On Friday, President Bush committed $2.5 million in military services to support the mission, and the U.S. government awarded $20.5 million in contracts to two U.S. companies to provide tents, electricity and other support. The European Union also announced it would spend $125 million to support the peacekeepers, but the promised aid falls short of the African Union's request for $220 million.

The conflict began in early 2003, when two rebel groups launched a revolt in western Sudan, saying they faced discrimination. They have accused the government of bombing villages and arming the Janjaweed militia to crush them. Sudanese officials blamed the rebels for starting the war and said the Janjaweed is made up of miscreants largely out of their control.