The Khartoum government is under intense international pressure to rein in alleged pro-government fighters accused of looting and burning farming villages and provide security for those displaced in the fighting in the remote area bordering Chad.
If not, the UN Security Council says, Khartoum could face unspecified sanctions.
"We thought we could have been sufficiently consulted before fixing the date in particular but nevertheless we will go," Ali Trayo, spokesman for Sudan Liberation Army (SLA), said on Thursday.
The secretary-general of the other main rebel group JEM, Bahar Idriss Abu Garda, said they would go to the talks, although the date might be problematic.
The African Union has proposed a 23 August date.
"Yes, we are going to the talks, but we have some remarks about the time they decided because we have a conference in Germany at same time," he said. "Because of that we want to postpone the time."
The SLA also said the date gave them little time to organise and inform their movement commanders scattered throughout Darfur, a remote area the size of France.
The SLA and JEM launched a revolt in February last year accusing Khartoum of neglect and of arming "militias" known as Janjawid to drive African farmers from their lands.
The UN threat has been slammed
by Sudan government supporters
Sudan denies the charge saying the Janjawid are outlaws, and that the international communitry has wrongly presented the conflict as a racial one when it is a war over land.
An alleged Janjawid leader recently told Aljazeera.net that the rebels started the conflict and tribes in Darfur are simply defending thelmselves.
However, the UN says the conflict has triggered the world's worst humanitarian crisis with about 200,000 refugees in neighbouring Chad.
Abu Garda also said the rebels had agreed with the World Food Programme (WFP) to give the UN body access to rebel-held areas in Darfur to distribute food.
"Our delegation in Asmara headed by our president and also the SLA agreed ... and we will commit ourselves to execute this.
"In our whole area the WFP are free to come and see the people," he said, adding they would be afforded full protection.
Over a million people have been
displaced by the Darfur fighting
But he added that the JEM could not protect them if the government bombed their areas despite an April truce signed in the Chadian capital N'Djamena.
"The government should commit itself to stopping any flyovers of our territories," he said.
The United Nations said in a statement from Geneva on Tuesday that Sudan had used helicopter gunships in fresh attacks in south Darfur.
The government denied the reports and the top UN official in Khartoum said they were still being checked.
But Human Rights Watch said atrocities like rape were still happening in Darfur, despite government promises to bring security to those displaced.
Sudanese President Umar al-Bashir said Western nations were exploiting the Darfur conflict to gain control of resources like oil and gold in the arid region.
"There is an agenda to seek for petrol and gold in the region," he told a women's union meeting convened on Darfur in Khartoum on Thursday.
Umar al-Bashir says the West is
trying to control Sudan's wealth
"This high life that they (the West) enjoy now is a result of the theft of the colonies and their riches and peoples," he said, with a specific reference to Britain.
Sudan's two main oil fields are in the south, although Khartoum is hopeful of more oil discoveries in Africa's largest country.
Meanwhile, Tanzania is considering a request by the African Union (AU) to send troops to Darfur, Tanzania's defence minister said on Thursday.
"I have been requested (for troops) but the decision has not yet been reached because the situation there is very fluid," Defence Minister Philemon Sarungi said, adding the government was assessing the situation in Darfur.
The AU has said it would send more than 300 troops to western Sudan to protect AU monitors there, but it is considering expanding its mission to about 2000 soldiers who would have a peacekeeping role.
So far only Rwandan and Nigerian troops had been picked to be part of the 53-member AU's force in Sudan.