Sudan has postponed a census that is crucial for the success of two upcoming national polls, the UN says.
There is little updated information on Sudan's population
The survey was delayed due to funding shortfalls, the United Nations stated.
Census officials accused Sudan's government of withholding the $30m it had pledged. The UN says the government is now committed to paying its share.
Originally due on 15 November, the census will now be held from 2 February 2008. People will only be eligible to vote if they take part in the census.
The UN Population Fund (UNFPA) is helping to organise the two-week census, the first since the January 2005 peace deal between the north's National Congress Party (NCP) and the former southern rebel group, the Sudan People's Liberation Movement (SPLM).
The deal ended decades of civil war and established the coalition Government of National Unity (GONU), paving the way for elections by 2009 and giving the south the right to decide whether to split from the north by 2011.
Since the last census in 1993 Sudan has changed dramatically - partly because of the 20-year war, in which two million people died - says the BBC's Amber Henshaw in Sudan.
There is little up-to-date information on population size, age, growth rates and geographical distribution.
These two polls will be key to the future of the country, our correspondent says.