Sudan has blocked a shipment of southern oil after Juba refused to pay customs fees, the foreign ministry said on Friday, escalating a row in which the south accuses Khartoum of sabotaging its economy. "Sudan has blocked the ship in Port Sudan ... When the ship leaves the port, the south has to pay the customs authorities. This is the first time they didn't pay," foreign ministry spokesman Al-Obeid Meruh told AFP. He had earlier said the 600,000 barrel crude cargo had been blocked because of the Juba government's refusal to pay the north's fees for the use of all its oil infrastructure, including its pipeline, refinery and Red Sea port, which is the south's only export terminal. However, Meruh confirmed that no agreement had yet been reached between north and south on transit fees, which is one of the most sensitive of Sudan's unresolved issues following the south's formal declaration of independence on July 9. He said Khartoum was asking for $32 dollars per barrel. The ministry of energy and mines in South Sudan, from which 80 percent of the divided country's total oil production of 470,000 barrels per day is pumped, accused Khartoum of delaying the negotiations to squeeze the south. "They want to stop the shipment so that it prolongs the whole (negotiating) process. Khartoum is trying to sabotage the economy of South Sudan," the ministry's undersecretary, David Loro, told AFP. He said a committee of southern officials was currently in Khartoum working to reach an agreement with the Sudanese government on the question of transit fees. South Sudan sold its July-lifting oil independently, for the first time, at international prices and apparently without interference from Khartoum, shipping around 3.2 million barrels from Port Sudan. Since then, however, tensions have flared over the issues of currency and oil transit fees. Both countries launched new currencies in July, and southern officials have voiced fears that Khartoum may flood the south with the old currency before it is withdrawn. Late last month, South Sudan's chief negotiator, Pagan Amum, warned Khartoum against starting "economic wars," and said the charges that it had imposed amounted to "daylight robbery." He said Sudan should set its transit fees according to "international standards," and cited the figure of $1.8 a barrel charged by other states with similar arrangements, reflecting how far apart the two sides are on the issue. North and South Sudan both depend heavily on their oil receipts, with Khartoum's cash-strapped government desperate to offset its loss of southern oil revenues, which represented some 36 percent of its income prior to partition. Just weeks before the south seceded, Sudan's President Omar al-Bashir threatened to deny the landlocked south access to the north's oil infrastructure if no deal was reached. The World Bank, meanwhile, warned last month that the Juba government urgently needed to develop the new nation's agricultural sector to lessen its reliance on oil, which accounts for more than 95 percent of its total revenues. As well as the differences between Juba and Khartoum on oil and currency, the two sides have yet to agree on the demarcation of their disputed common frontier and on the future status of the bitterly contested Abyei border region.