South Sudan said that blocks B1 and B2 were open for direct negotiation after talks with Total, Tullow Oil and the Kuwait Foreign Petroleum Exploration Co. broke down over "irreconcilable differences."

"We have decided ... to open opportunities to other potential investors," Ezekiel Lol Gatkuoth,South Sudan's minister of petroleum, said in a statement dated April 22.

Blocks B1 and B2 were once part of the 120,000 sq-km area known as Block B, which was divided into three licenses in 2012 and is thought to be rich in hydrocarbons, although very little drilling has been done there. Land-locked South Sudan, which split from Sudan in 2011 after decades of conflict, has been mired in civil war since President Salva Kiir ousted former Vice President Riek Machar in 2013.

The unrest threatens the world's youngest country's plans to more than double crude production to 290,000 barrels per day (Mbbl/d) in the 2017/2018 fiscal year.

The main oil firms involved in South Sudan, which produced about 245 Mbbl/d until fighting flared at the end of 2013, are China National Petroleum Co., Malaysia's state-run oil and gas firm Petronas, and India's ONGC Videsh.