The Sudanese government said talks to end violence in Darfur would resume at the end of February, but rebels said they had not been told of the date and would need more time to prepare themselves for any talks.
The rebel Sudan Liberation Movement (SLM) said a return to talks depended on the government creating a "conducive atmosphere", and that the African Union, which is sponsoring the talks, had not given it a date.
SLM spokesman Adam Ali Shugar said on Sunday the government had within two weeks to withdraw from areas it had captured since a much-violated ceasefire was signed, and respect a no-fly zone, before the rebels would consider a return to talks.
"We have not received any notification from the African Union (AU) regarding the restarting of the talks," he said.
"If the government delivers on its pledges and creates a conducive atmosphere then we will return to talks," he said.
SLM Chairman Abd al-Wahid Muhammad Ahmad Nur said the AU had to force the government to implement agreements signed in November on security and humanitarian issues for peace talks to have any meaning.
Twenty days preparation
Nur said the SLM also needed at least 20 days to prepare for any talks.
A Chadian mediator last week said the Sudanese government had respected conditions set by the rebels and a return to peace talks in Abuja was certain.
Majdhub al-Khalifa, the head of the government negotiating delegation, said late on Saturday the AU had told the government peace talks would resume at the end of February.
The UN has warned of the threat
of famine in Darfur
The United Nations on Friday warned of a new threat of famine in Darfur, where rebels took up arms two years ago.
It said as many as 4 million people might soon be in desperate need of assistance.
Aid workers, relief helicopters and food trucks were under fire from government forces and rebels, the UN added.
Rebels need pressure
The Sudanese government called on the international community to exert pressure on rebel groups to resume talks.
"We have respected the ceasefire - primarily for the safety of our own civilians - and grounded our military aircraft in a show of good faith," al-Khalifa added in a statement on Saturday.
"Pressure needs to be exerted upon the rebels to ensure the success of these talks."
"Pressure needs to be exerted upon the rebels to ensure the success of these talks"
Majdhub al-Khalifa, head of Sudan's negotiating team
The SLA last week claimed it had spotted a government military plane in northern Darfur.
Darfur rebels began their uprising against Khartoum and exploited the dispute over grazing land.
The dispute over land started between subsistence farmers and nomadic tribes, but rebels say they took up arms because of the government's marginalisation of the arid province.
Khartoum says rebels want to take control of the province, thus making it a power struggle more than anything else.