Southern Sudan's government says the Sudanese president will give a speech at this weekend's independence day celebrations.
Monday's announcement comes just days after President Omar al-Bashir said his army would continue an offensive in the northern state of South Kordofan.
Hostilities there against southern-aligned forces have displaced more than 70,000 people.
Al-Bashir's statement makes it unlikely the two governments will reach a cease-fire by independence day on Saturday.
Western advocacy groups have warned that the northern government is attempting ethnic cleansing and even genocide in the region.
Two decades of civil war with northern Sudan decimated the oil-rich south and left more than 2 million dead.