The 26-year-old socialite -- who has promised to use her celebrity status for good causes -- was supposed to pack her bags for the African country next month. On her itinerary: visits to schools and health-care clinics.

"I'm scared, yeah. I've heard it's really dangerous," Hilton told Newsweek magazine earlier this month. "I've never been on a trip like this before."

Hilton announced the mission in September, several months after serving a 23-day jail sentence for violating probation in an alcohol-related reckless driving case.

"There are a lot of bad people in L.A. Before, my life was about having fun, going to parties -- it was a fantasy," she told Newsweek. "But when I had time to reflect, I felt empty inside. I want to leave a mark on the world."