South Sudan's Kiir to visit Sudan ahead of oil stoppage deadline KHARTOUM/JUBA (Reuters) - South Sudan's President Salva Kiir will visit Sudan on Tuesday for talks with President Omar Hassan al-Bashir, officials said on Sunday, as the long-time foes seek to avert a halt of vital cross-border oil flows. Diplomats hope what is only Kiir's second visit to Khartoum since South Sudan's secession in 2011 will help build trust between the neighbors, who fought one of Africa's longest civil wars that ended in 2005. Both countries agreed in March to defuse tensions and resume oil exports from landlocked South Sudan through the north, its only route to market. But Sudan has threatened to halt oil flows by September 6 unless Juba cuts ties with rebels operating across the disputed and unmarked border. South Sudan denies providing them any support. Kiir and Foreign Minister Barnaba Marial Benjamin will travel to Khartoum to discuss implementing the March agreement with Bashir, South Sudan's foreign ministry spokesman Mawien Makol Arik said. Sudan's state news agency SUNA also reported the planned visit, saying both heads of states would discuss bilateral cooperation. It gave no more details. The African Union has stepped up efforts to prevent the production shutdown, starting an investigation of the Sudanese allegations. South Sudan relies heavily on oil exports and the shut down could have serious economic and political implications. Diplomats doubt Sudan will actually close the two cross-border pipelines as it needs South Sudan's payment of oil transit fees. Khartoum has several times extended a deadline threatening a halt of oil flows. Reporting by Khalid Abdelaziz in Khartoum and Andrew Green in Juba; Writing by Ulf Laessing; editing by David Evans