The Darfur rebel Sudan Liberation Movement/Army (SLM/A) on Sunday asked the African Union to give it ample time to hold its general conference before resuming the talks in Abuja, the Nigerian capital.
African Union spokesman in Khartoum Baba Gana Kingibe alleged in a statement on Sunday that the rebel group had killed an undetermined number of Arab nomads, abducted seven and stolen 3100 camels in a 25 August attack.
The African Union "condemns not only the provocative banditry of the SLA/M but also their continuing refusal to cooperate" with peace mediators, the statement said.
Such an incident "not only destabilises the quiescent security situation on the ground but also impacts negatively on the talks," it said.
The government and rebel groups are due to kick off a new round in their floundering peace negotiations on 15 September in Abuja.
While the AU has commended the Sudanese government's commitment to ensuring the talks yield a final agreement, it has become increasingly annoyed with the rebels' reluctance to work towards a deal.
The Sudan Liberation Movement is
accused of recent attacks
Fighting in Darfur broke out in February 2003 when an uprising representing the mainly black population of the region led Khartoum to unleash Arab militias known as Janjaweed, which have been accused of torture, rape and intimidation.
Some 300,000 people have been killed in the conflict which has displaced more than two million others.
Former rebels in Khartoum
Also on Sunday, a contingent of 1500 soldiers from Sudan's former southern rebel group arrived in Khartoum to form the first joint unit with government troops, a key feature of the January north-south peace agreement.
The soldiers, who set up camp in a base 10km southeast of Khartoum, are from the Sudan People's Liberation Movement (SPLM) that fought a bloody 21-year civil war against the government.
They were greeted by Sudanese intelligence chief Mohammed Hassan Fadel and will soon establish the first Joint Integrated Unit with an equal number of northern government troops, an AFP correspondent reported.
Under the accord Khartoum and the SPLM signed on 9 January, joint units are to be formed to ensure compliance with the permanent ceasefire.