South Sudanese Vice President Riek Machar arrived in the Sudanese capital on Sunday seeking to ease tensions after Khartoum threatened to halt oil flows worth billions of dollars to both impoverished neighbours. Machar landed at the airport in Khartoum, an AFP correspondent reported, and was to head immediately to a conference hall on the banks of the Blue Nile for talks with his northern counterparts. Shipments from Sudan of South Sudanese oil resumed about nine days ago after resolution of a year-long fee dispute, and despite uncertainty after President Omar al-Bashir ordered the oil flow stopped. The landlocked South voted to split from Sudan two years ago, under a peace deal which ended a 22-year civil war. South Sudan left with most of the formerly-united country\'s oil production but pipelines and the Red Sea export terminal remained in Sudan. The Juba government halted its crude production early last year in a dispute over how much it should pay Khartoum to use the export infrastructure. A March deal finally saw Juba resume pumping oil which flowed slowly toward Port Sudan where stocks built up for export. But on June 8 Bashir abruptly ordered the pipeline shut after warning Juba over backing rebels in the north. South Sudan denies supporting cross-border insurgents. A careful shutdown requires several weeks to avoid damaging the infrastructure, giving diplomats time to try to resolve the deadlock.