A new report from the U.N. secretary-general says nearly half a million people were displaced in Darfur last year, the highest number in a decade.

Ban Ki-moon's latest update on the chaotic region of western Sudan comes as the U.N. begins meeting with Sudanese officials on plans for an exit strategy for the more than 20,000-strong peacekeeping mission.

Tensions have been high between the U.N. and Sudan, especially over a Human Rights Watch-documented mass rape of more than 220 women and girls in a Darfur village last year.

Ban's report says he deeply regrets that the U.N. has not been able to access the village.

More than 450,000 people were displaced throughout Darfur last year, the most since 2004.