South Sudanese President Salva Kiir has arrived in Sudan's capital, Khartoum, to meet Sudanese President Omar Bashir.
The two were expected to discuss the current conflict in South Sudan between the central government in Juba and the forces of Riek Machar, Mr Kiir's former vice president who was dismissed from his cabinet in July.
Juba accused Mr Machar of an attempted coup.
The two leaders also likely will address security issues along their shared oil-rich border region and the ongoing tensions in the border area of Abyei.
The last time the two met was in January when Mr Bashir visited Juba.
Both countries have suffered from instability and sporadic violence since they split in 2011.