A senior African Union official hosting crisis talks on Darfur says continual violations in ceasefire agreements are damaging a fragile peace process.
More than two million have been displaced by the violence in Darfur
Peace talks are under way in Abuja in Nigeria between the Sudanese government and rebels from the western region.
But, despite a positive end to earlier discussions, the mood has been soured by renewed violence.
The aim is to find a political solution to the conflict in Darfur that has claimed about 70,000 lives.
Sam Ibok, the chairperson of the African Union-sponsored talks, says he hopes sanctions can be introduced to punish those who violate ceasefire agreements.
"We take strong exceptions and we are hoping that we will move into a situation... whereby measures or sanctions can be put in place for those who violate the agreements," he said.
Earlier this week the US said international efforts to tackle the crisis were "getting nowhere".
The US ambassador to the UN, John Danforth, said all sides in the conflict shared responsibility for the violence.
The civil conflict began in early 2003, when rebel groups accusing Khartoum of neglecting the region began attacking government targets.
The government responded by mobilising Arab militias, which have been accused of widespread atrocities.
More than two million people have been made homeless as a result of the violence.
Last month delegates at the peace talks signed two documents pledging to improve security in Darfur and guaranteeing humanitarian access to civilians caught up in the crisis.
The BBC's Anna Borzello in Abuja says there was hope that this move would be a real step forward.
And she says the success or failure of the current round of talks also has implications for credibility of the AU itself, and its promise for African solutions to African problems.
But despite both remaining hopeful that a peaceful settlement can be reached, neither the government nor the rebels appear to be in a conciliatory mood, she says.