The arrival of Major General Bakri Hassan Saleh and other military chiefs on Wednesday is being seen as a sign the talks have entered a crucial stage.
Sudan's Vice President Ali Osman Taha, and John Garang of the Sudan People's Liberation Army (SPLA) are meeting in the Kenyan town of Naivasha to revive their country's peace process.
SPLA spokesman Samson Kwaje said the talks were getting very serious.
"It will all depend on the flexibility of the government, but the SPLA is determined to make difficult decisions for the sake of peace in Sudan," he said.
And Garang himself described the chances of pushing the peace process forward as "excellent".
The 20-year conflict between the government in Khartoum and the SPLA is estimated to have killed at least 1.5 million people.
The peace talks stumbled late last month when Khartoum opposed a draft deal which provided for a separate army for the south during an interim period.
Khartoum argued the clause would pave way for the south's immediate secession.
Mediation sources said one of the key issues on the table was "a joint command board to solve the problem of either two armies or one army during the interim period" of self-rule for the south.
"Khartoum is faced with a scenario of sharing power with the southern rebels and that is why the talks depend on it. It will also have to sacrifice," said the source.
Conflict has raged in Darfur since
Taha and Garang have also been negotiating how to share resources, particularly oil revenues, during the south's period of self-rule, which will take effect only after a peace pact has been signed.
And the two sides are also wrangling over three disputed areas - the Southern Blue Nile State, Abyei, and the Nuba Mountains - where the SPLA is active.
In a separate development, a Sudanese official said on Wednesday that a government warplane killed 26 civilians in western Sudan last month after it mistakenly identified them as rebel forces.
The governor of West Darfur State, Major General Suleiman Abd Allah, told Al-Ayam newspaper a committee had been set up to investigate the incident in the Habeela area.
Another 32 people were also wounded in the attack carried out by an air force plane, said the governor.
Abd Allah also said the government decided to pay blood money to the families of those killed, and the first portion of the compensation had already been paid.
Conflict has raged in Sudan's western Darfur region since February.
Rebels calling themselves the Sudan Liberation Movement (SLM) say they are fighting for an end to marginalisation and neglect of the large, impoverished region.
The Sudanese government announced last week it and the SLM had signed a six-week ceasefire at a meeting in Chad.