The conflict in Sudan's western region of Darfur can only be solved through cessation of hostilities between the warring groups, which should then engage in dialogue, Jan Eliasson, the United Nations Secretary-General's special envoy for Darfur, said.

"We need to try our very best from all corners to encourage a political process," Eliasson told reporters in the Sudanese capital, Khartoum, where he met Sudan's President Omar El Bashir and other officials. "If we don’t reach that goal, we run the risk of the Darfur nightmare continuing year after year," Eliasson said.

Fighting in Darfur between rebel and government forces since 2003 has caused the death of more than 200,000 people and forced another 2.5 million from their homes, some into neighbouring Chad.

Violence has persisted in Darfur despite a peace agreement reached in Abuja, Nigeria, in May 2006 between Khartoum and one of the main rebel groups, which took up arms against El Bashir’s government, alleging decades of marginalisation and oppression. The government responded with a military crackdown and has allegedly sponsored the mainly Arab Janjawid militia, which is accused of committing atrocities against unarmed non-Arab civilians.

On Wednesday, Bill Richardson, governor of the US state of New Mexico, said during a visit to Sudan that the Darfuri rebel groups that had not signed the Abuja peace pact had agreed to a ceasefire with the government.

Eliasson, however, said he was uncertain about the viability of a ceasefire agreement among Darfur’s increasingly fragmented rebel groups.

"I don’t know to what degree the non-signatories in Darfur are fully committed to this," said Eliasson. "It is not completely clear. I can only say that the United Nations would welcome any effort to reduce the level of violence," he said.

The UN Security Council voted in August 2006 to send blue berets to the war-torn region to bolster the African Union's (AU) peacekeeping mission, which has been hamstrung by funding problems and a weak mandate. But despite intense international pressure, Sudan has rejected a UN presence. The government, has, however, said it would allow technical UN support personnel to be deployed to Darfur to help the AU.