The U.S. military says it is readying plans to help airlift Rwandan troops for an expanded African Union mission in Sudan's western Darfur region.

Military officials say U.S. air force personnel arrived in Rwanda's capital, Kigali, Thursday, preparing to begin the airlift in coming days.

It says the two-week operation will involve 120 airmen stationed in Germany.

Rwanda has promised to send about 300 soldiers to reinforce a team monitoring a ceasefire between militias and rebels in Darfur.

Meantime, the United Nations refugee agency says it is boosting operations in Darfur to give protection and humanitarian aid to an estimated 1.5 million displaced people.

The group says it is also overseeing camps in Chad for another 200,000 people fleeing violence in Darfur.