The Nigeria talks mediated by the African Union (AU) have been hampered by an argument over the role of Chad that has yet to be resolved, but the parties have resumed face-to-face talks over a declaration of principles after the AU increased pressure.
"The chairman [of the mediating team] has set a deadline for tomorrow for agreeing on the declaration and we are hopeful that the target can be met," said Khalil Abdelrahim, Sudan's ambassador to Nigeria, on Saturday.
"We have spent two weeks on something we had hoped to resolve in two or three days so a lot of time has been wasted, but in the past two days there has been progress," he added.
Ahmed Hussein Adam, spokesman for the rebel group Justice and Equality Movement (JEM), expressed a similar view.
"I am optimistic. We are negotiating and engaging and that is a good sign," he said.
According to the format set by the mediators, the parties must agree on a series of basic principles before they can tackle substantive issues such as power and wealth sharing and security arrangements for Darfur.
Rebel movements in the vast western region of Sudan took up arms against the central government in early 2003 over what they saw as neglect and discrimination.
"We have spent two weeks on something we had hoped to resolve in two or three days so a lot of time has been wasted, but in the past two days there has been progress"
Sudan's ambassador to Nigeria
The conflict has killed tens of thousands and driven more than two million people from their homes into overcrowded refugee camps inside Sudan and in neighbouring Chad.
The JEM, whose leadership has fallen out with Chad, accuses the country of being a "peace-spoiler" and objects to its presence at the talks.
But the mediators and Chad itself say it has played a role in earlier rounds of talks and must be a part of any final settlement due to its long border with Darfur and the presence on its territory of hundreds of thousands of refugees.
The JEM spokesman said on Saturday that the movement is still awaiting a decision on the Chad argument from Nigerian President Olusegun Obasanjo, who waded into the dispute earlier this week.
Chadian delegates were present at a negotiating session late on Friday between representatives from the government, the JEM and larger rebel group the Sudan Liberation Army (SLA).
Outstanding hurdles that still must be overcome before the declaration of principles can be signed include a rebel demand that the unity of Sudan not be taken for granted but be part of a new social, cultural and political contract.
The Darfur conflict has created
more than two million refugees
The JEM also wants the declaration to define crimes
perpetrated in Darfur as war crimes and genocidal acts, and to say international courts should prosecute suspects rather than Sudanese courts, as the government wants.
The United States has said genocide occurred in Darfur, although the United Nations has stopped short of using the word.
The International Criminal Court has launched an investigation into suspected war crimes in Darfur, which Khartoum is resisting.