United Nations: When Sudan holds its first democratic elections in over two decades next year, people in the conflict-ravaged region of Darfur may be left out, the UN peacekeeping chief said on Friday.

"The contested census, large-scale displacement and volatility - particularly in the area bordering Chad, create enormous risks that the people of Darfur will not be in a position to participate in the electoral process," UN Undersecretary-General Alain Le Roy said.

"This would further disenfranchise millions already disempowered by conflict," he told the UN Security Council, adding that the election results will have an "enormous impact" on the distribution of political power in Darfur where millions of internally displaced refugees live in camps.

Last month Sudan said its nationwide elections would be delayed for two months to April 2010, the second time the date has been changed.

The poll in Africa's largest country will be the first in more than 20 years under a 2005 peace deal that ended over two decades of civil war between north and south Sudan.

The conflict in Darfur in western Sudan dates back to 2003, when mostly non-Arab rebels took up arms against Khartoum, accusing it of neglecting the region.

Estimates of the death count in Darfur range from 10,000 according to Khartoum, to as high as 300,000 according to UN humanitarian chief John Holmes.

US Deputy Ambassador Rosemary DiCarlo told the council that the possibility that Darfuris would be left out of the electoral process was a "real concern".

She also criticised Khartoum for delays in issuing visas to staff of the joint UN-African Union Mission in Darfur, known as Unamid.

A Sudanese envoy told the council that Khartoum was not trying to delay Unamid's deployment and would "do its best" to ensure that the force is functioning as soon as possible.

Russia's special envoy to Sudan Mikhail Margelov highlighted African Union concerns about the International Criminal Court's indictment of Sudanese President Omar Al Bashir for war crimes earlier this year, which prompted Khartoum to expel 13 foreign humanitarian aid organisations.