Sudanese rebels have reacted angrily to the decision to adjourn the peace talks in Kenya for three weeks.
The vice president (right) is crucial to the talks
Mediators say the postponement until 17 February will allow Muslim negotiators like Vice-President Ali Osman Mohamed Taha to go on the Hajj pilgrimage.
Sudan Peoples Liberation Army spokesman Samson Kwaje has told the BBC the adjournment is a delaying tactic by the government.
Both parties have signed a deal on a 50-50 split of the country's wealth.
"During Christmas we only had a break for one day. We were hoping to reach a comprehensive agreement by the end of the month but this will now be delayed," said Mr Kwaje.
He said the SPLA had disagreed with government negotiators on their proposals over the disputed regions of Abyei, Blue Nile and the Nuba mountains.
But Kenyan chief mediator Lazarus Sumbeiywo told the BBC there were no specific obstacles at the talks.
"The issues are difficult on both sides and I am not disappointed with the progress reached so far," he says.
Last week, US presidential envoy John Danforth said he believed a final deal to end the 20-year war was in sight.
But despite the peace talks, fighting in Darfur in western Sudan has intensified in recent months prompting more than 100,000 refugees to flee into Chad.
On Monday, witnesses in Darfur who had fled to Chad, told of government planes bombing their villages and militias attacking them.
Darfur residents have fled to Chad
They accuse the government of practising a scorched earth policy in fighting a rebellion by Sudan Liberation Army rebels who say they want to end discrimination in Darfur.
The United Nations refugee agency says conditions for the refugees are harsh, with scorching sun during the day, and bitter cold at night.