Obasanjo on Thursday dropped in on the peace talks, which are taking place in a luxury hotel in the Nigerian capital Abuja, and added pressure on delegates from two rebel movements to quicken the pace of negotiations.
The conflict has killed tens of thousands and driven more than 2 million from their homes into overcrowded refugee camps inside Sudan and in neighbouring Chad.
"He told us to think about the suffering of refugees ... He asked the movements to be more flexible," said Abdelrahman Musa Abakar, spokesman for the Sudan Liberation Army (SLA) delegation.
"He told us that Nigeria has greater problems than Sudan and our task is not more difficult than what he got when he came to power," Musa said by telephone, adding that his movement had drawn encouragement from the meeting.
"We didn't feel it was pressure, I would call it a reminder," he said.
Obasanjo is chairman of the African Union (AU), which is leading the mediation team at the peace talks.
The SLA and a smaller rebel group, the Justice and Equality Movement (JEM), took up arms in early 2003 accusing the Sudanese government of discrimination and neglect. The rebels say Khartoum reacted by backing Arab militias to drive non-Arabs from their villages.
Four previous rounds of peace talks in Abuja failed.
The fifth round began three weeks ago and the parties have yet to agree on a broad declaration of principles. Progress has been hampered by wrangling over the presence of representatives from Chad, which has poor relations with the JEM, and from Eritrea, which is at loggerheads with the Sudanese government.
In addition, divisions among rebel ranks have cast doubt over whether any deal struck in Abuja would carry much weight among fighters inside Darfur.
However, the AU says progress has been made and emphasises that the three parties -- the government, SLA and JEM -- are holding face-to-face talks. Objections to the Chadian and Eritrean presences have been quietly dropped.
- Reuters - Thomson Reuters Foundation
- For more humanitarian news and analysis, please visit https://www.trust.org/alertnet