Northern and southern Sudanese leaders on Saturday said they would consider forming a confederation or a common market if southerners chose to declare independence in an upcoming referendum, Reuters reported. Citizens of the country's oil-producing south are six months away from a vote on whether to stay part of Sudan or split away as an independent state -- a plebiscite promised in a 2005 accord that ended decades of north-south civil war. Leaders from the country's dominant northern and southern parties on Saturday started formal negotiations on how they would divide oil revenues and other issues after the referendum. They told reporters at the launch they would consider four options suggested by an African Union panel led by former South African president Thabo Mbeki. In one option "we considered the possibility of the creation of two independent countries which negotiate a framework of cooperation, which extends to the establishment of shared governance institutions in a confederal arrangement," said Mbeki, who spoke at the launch in Khartoum. Another option was for two separate countries with shared "soft borders that permit freedom of movement for both people and goods," said Mbeki. The other two options, he added, were for total separation - - with citizens needing visas to cross the border -- and for continued north-south unity, if southerners chose that option in the referendum. "These (the four options) will be part of the issues to be discussed by both parties," Sayed el-Khatib, a senior member of north Sudan's National Congress Party, (NCP) told reporters. Pagan Amum, the secretary general of the south's dominant Sudan People's Liberation Movement (SPLM), said the referendum would allow the south to "reset" its troubled relationship with the north, whether southerners chose unity or separation. "If the choice is separation, then we will be ensuring that there will be good cooperation between the two independent states. It could take the form of a confederation. It could take the form of a common market," he said. The parties said they would spend the next months working out how they would share out oil and other assets, as well as the burden of Sudan's national debt, after the vote. -- SPA