Salva Kiir, South Sudan's president, has flown to Khartoum to hold bilateral talks with President Omar al-Bashir to discuss the outstanding issues that remain following secession in 2011.
Kiir’s one-day visit came at Bashir's invitation, Ali Karti, Sudan's foreign minister, said at the airport.
"Sure, it is not enough to discuss all the outstanding issues but it will solve some of them and it shows the goodwill of the two countries," he said.
In a statement issued after he left for Khartoum, Kiir spoke of a "new spirit of cooperation" that he expected would resolve some key issues.
While Sudanese officials and media also spoke positively, similar optimism has prevailed before only to see the two countries - whose border clashes early last year stirred fears of wider conflict - fail to implement agreements.
Halted oil exports
In March the two countries signed an agreement to resume halted oil exports from the landlocked South Sudan, on which it depends for much of its economy.
However in June Sudan threatened to stop oil flows by September 6 unless South Sudan cut ties and purportedly stopped arming rebels in the north, in an attempt to destabilise its former foe.
Both countries accuse the other of arming rebel groups to continue conflict by proxy. The neighbours fought one of Africa’s longest civil wars, ending in 2005 with the signing of the internationally brokered Comprehensive Peace Agreement.
Talks are expected to centre on a range of post-secession issues, which remain unresolved despite a number of high-level summits that have taken place before and after South Sudan gained independence.
These include most notably cooperation on oil sharing, security issues, citizenship, and the political stalemate surrounding ownership of the oil rich border area Abyei, which is claimed by both countries.
A vote was planned in January 2011 for Abyei’s residents to decide whether they wanted to join north or south Sudan, but it never took place.
Last year, Thabo Mbeki issued a proposal approved by the African Union's Peace and Security Council to hold a referendum this October.
The referendum would exclude the majority of the nomadic Misseriya who spend a few months of each year in Abyei for grazing. The Dinka Ngok who reside in Abyei were granted the right to vote by Juba.
Sudan rejected the plan and the AU appears to have put its implementation on hold. The UN Security Council is yet to make its position formally known.
Sudan has warned South Sudan against unilaterally holding a referendum in Abyei and vowed not to recognise its results.