UNITED NATIONS (AP) — The U.N. Security Council is extending for another year the U.N. mission in Sudan that backs up the 2005 agreement ending the north-south civil war.

The council's 15 members voted unanimously Thursday to keep the mission known as UNMIS going until April 30, 2011 "with the intention to renew it" again.

A referendum is expected to be held early next year to determine whether the south secedes from Sudan and the future of the disputed oil-rich region of Abyei.

The Abyei issue threatened to derail the peace agreement in Sudan that ended two decades of civil war between the north and south that killed at least 2 million people.

Secretary-General Ban Ki-moon expressed concern there has been "little concrete progress" toward preparing for the referendum.