Sudan on Sunday said it has started confiscating some oil exports from South Sudan it believes it is due to meet unpaid transit fees but will not shut down a pipeline carrying the southern state's oil.
South Sudan became independent in July under a 2005 peace deal with Khartoum that ended decades of civil war killing two million people but both sides have failed to sort out a long list of disputes.
The biggest conflict is over oil revenues - the lifeline of both economies. Land-locked South Sudan got two thirds of the country's oil output but needs to pay fees to use northern export facilities.
Both countries have failed to agree on a transit fee but will resume on Tuesday talks sponsored by the African Union in Ethiopia. Previous rounds ended with the parties still wide apart.
Sudan has started confiscating southern oil to compensate for Juba's failure pay a fee to use Khartoum's pipeline and the Red Sea port of Port Sudan, members of the northern delegation for the talks in Addis Abeba said.
South Sudan pumps around 350,000 barrels per day (bpd), officials have said. Sudan produces 115,000 bpd in its remaining fields but needs it entirely for domestic consumption.
"Since early December we've started taking part of our share after the southern government refused to agree on a deal for a transit fee," Saber Mohammed Hassan, a member of the delegation, told reporters.
He said Khartoum was now demanding a pipeline fee of $36 a barrel, up from an initial demand of $32.
Delegation member Zubair Ahmed Hassan added Khartoum was taking some southern oil to use for northern refineries but gave no volumes.
South Sudan has accused Khartoum of blocking oil exports of 3.4 million barrels in Port Sudan and asking foreign oil firms to divert some oil to refineries in Khartoum and El-Obeid.
In a second demand, Khartoum wants Juba to pay a total of $1 billion for transit fees since July, said deputy central bank governor Badr el-Din Mahmoud, another delegate.
He said South Sudan also owed Khartoum another $6 billion in debt. "The South has sent us a letter demanding $5 billion but this amount is not correct. We actually demand from the South $6 billion," he said.
Sudan's government is under pressure to overcome a severe economic crisis after losing the southern oil which made up 90 percent of the country's exports. It generated $5 billion in oil revenues in 2010.
South Sudan has refused to shoulder Sudan's foreign debt pile of almost $40 billion which has been a burden for the economy for many years in addition to a US trade embargo deterring most Western firms.
South Sudan has accused Khartoum of "stealing" its oil exports at the northern port of Port Sudan by ordering its security services to load 650,000 bpd of southern oil worth $65 million on a Sudanese tanker.
"The Government of Sudan has chosen to steal this oil in broad daylight just days before its own proposed commercial oil negotiations with the Republic of South Sudan," South Sudan's oil minister Stephen Dhieu Dau said in a statement on Saturday.
He said the oil pipeline would be closed within days since storage capacity was filling up in Port Sudan but Azhari Abdalla, director general of Sudan's Oil Exploration and Production Administration, dismissed this.