A five-member panel to investigate whether genocide has taken place in Darfur has been appointed by United Nations Secretary General Kofi Annan.
Some 1.4 million people have been displaced in the conflict
The commission has been given three months to report its verdict about events in the western Sudanese region.
The United States has already declared the attacks in Darfur to be genocide, and human rights organisations have said they amount to war crimes.
An estimated 50,000 people have died in the past year and a half in Darfur
Some 1.4 million have also been made homeless as a result of attacks by pro-government Arab militias.
The Janjaweed are accused of killing thousands of black African civilians and emptying villages as part of a campaign against rebels in Darfur.
The commission includes human rights and legal experts from Peru, Egypt, Pakistan and Ghana and is chaired by Italian law professor Antonio Cassese, who was president of the UN war crimes tribunal for former Yugoslavia from 1993-1997.
They will leave shortly for Sudan.
European diplomats and the United Kingdom have fallen short of saying genocide is taking place.
Mr Annan has also refused to use the term genocide, which would carry a legal obligation to act.
Sudan's Foreign Minister Mustafa Osman Ismail has accused the US of using the humanitarian problem in Darfur for its own political purposes.
Last month the UN Security Council adopted a resolution which threatened oil sanctions against Sudan if it did not reign in the militias. It also called for the investigation into genocide.
Earlier this week, UN special envoy Jan Pronk told the UN's Security Council that Sudan's government has failed to keep its promise to end violence in Darfur over the past month.
He said attacks on civilians continued and that both pro-government forces and rebel groups had broken a truce.
Mr Pronk said the army had continued its attacks, sometimes with helicopter gunships and neither the government nor the rebels had respected the ceasefire signed on 8 April.
Sudan has now said it will welcome more troops from the African Union.
But the UN envoy said these troops should not only monitor the ceasefire but ensure the safety of the displaced, oversee the disarming of fighters and act as a buffer between civilians and possible attackers.
Libya is planning to host a mini-summit on the Darfur crisis later in October.