South Sudan border row 'causing shortages'
A blockade along the border between north and South Sudan is causing a shortage of goods in the south, a southern minister has told the BBC.
Northern officials deny the Khartoum government has closed the border.
South Sudan is due to become independent in July and relations with the north are strained.
The two sides are to resume separation talks but disagreement remains on sharing oil revenues and the border region of Abyei, claimed by both.
Luka Biong, a southern minister in the federal government, told the BBC the border blockage was making life very hard for the southern states near the internal border.
Despite Khartoum's denial of any sort of economic embargo, there are many reports of trucks being stopped from travelling to the south.
Mr Biong said in the short term the blockage would hurt South Sudan, but in the long term it would damage the northern economy as southerners would look to supply themselves elsewhere.
Some southern leaders have accused President Omar al-Bashir's National Congress Party of closing the border, though the party denies this.
Mr Biong was more cautious, saying it could be a policy or the behaviour of isolated individuals at the local level.
Whatever the case, the situation is further degrading the relationship between the two parts of the country.
The two sides are due to resume critical pre-separation negotiations on Thursday but there is still substantial disagreement on issues such as oil and citizenship and about the border region of Abyei.
Both Sudan and the South are reliant on their oil revenues, which account for 98% of South Sudan's budget. But the two countries cannot agree how to divide the oil wealth of the former united state. Some 75% of the oil lies in the South but all the pipelines run north. It is feared that disputes over oil could lead the two neighbours to return to war.
Although they were united for many years, the two Sudans were always very different. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.
Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.
The health inequalities in Sudan are illustrated by infant mortality rates. In South Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.
The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.
Throughout the two Sudans, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.
Conflict and poverty are the main causes of food insecurity in both countries. The residents of war-affected Darfur and South Sudan are still greatly dependent on food aid. Far more than in northern states, which tend to be wealthier, more urbanised and less reliant on agriculture.