South Sudan urged the Khartoum government on Monday not to start \"economic wars\" over currency and oil transit fees, saying that the current charges that it has imposed amount to \"daylight robbery.\" Negotiations between north and south on key outstanding issues, which were suspended shortly before South Sudan\'s formal declaration of independence on July 9, are due to resume soon, chief southern negotiator Pagan Amum told reporters in Juba. But they look set to do so in an atmosphere of growing tension, with each side having since then taken unilateral steps on oil and currency, both highly sensitive issues for the two cash-strapped governments. Amum said Khartoum had imposed a transit fee of $22.8 per barrel on oil the south sends through its pipelines, Juba\'s only existing export route, compared with fees of $1.8 a barrel charged by other states with similar arrangements. \"This is nothing but robbery in broad daylight. I would like to take this opportunity to appeal to Khartoum not to start economic wars with South Sudan,\" he said. The Sudanese parliament on Thursday approved a law imposing fees on the south\'s use of northern oil infrastructure, but the finance minister said the charges would be determined in negotiations with the south. Meanwhile, southern officials announced earlier in the week that South Sudan had independently sold its first shipments of oil. Separately, Amum claimed that Khartoum\'s decision to launch a new currency on Sunday, just days after the south began circulating its own money, was a \"hostile act\" that violated a prior agreement by the Sudanese government not to do so until six months had passed. \"This is a hostile act... (that) is contrary to our emerging as two states on good terms,\" he said. There are widespread fears in Juba that Khartoum will refuse to buy back the estimated two billion old Sudanese pounds in circulation in the south, and that it may even flood the south with the old currency before it is withdrawn. But the governor of Sudan\'s central bank sought to allay such fears on Sunday, saying the bank was ready to negotiate with Juba about redeeming the old money. South Africa\'s former president Thabo Mbeki, who headed the African Union team mediating the Sudan negotiations in Addis Ababa prior to independence, met President Omar al-Bashir in Khartoum on Sunday, and is due to meet Amum in Juba on Tuesday. His talks with Bashir focused on the unresolved issues between north and south, notably future security along the volatile north-south border and financial arrangements, according to the official SUNA news agency. Amum, who led the southern delegation during the inconclusive Addis Ababa negotiations, was on Saturday reinstated as minister of peace and implementation of the 2005 peace accord, after unexpectedly resigning earlier this month.