"It will not be the end of May, it will be in June," said el-Ghassim Wane, a senior AU official.
He said the exact date would be announced on Thursday during an international donors' conference aimed at supporting the pan-African body's peace mission in Darfur.
Another AU official, speaking to AFP on condition of anonymity, said the resumption in talks would not begin "before June 10" for logistical and organizational reasons.
The May 30 resumption date had been announced on May 17 in Tripoli after an African mini-summit at which leaders from around the continent urged the sides to return to the AU-sponsored, Nigerian-hosted peace talks.
Darfur's two main rebel groups, the Sudan Liberation Movement (SLM) and the Justice and Equality Movement (JEM), did not attend that meeting but said they were ready to take part in the talks aimed at ending the crisis.
The negotiations broke down in December due to repeated violations of an April 2004 ceasefire.
An estimated 300,000 people have been killed and 2.4 million displaced since Khartoum launched a crackdown on an uprising by ethnic rebels in February 2003.