African Union mediator Thabo Mbeki was expected in the Sudanese capital Thursday night to help push Sudan and South Sudan back to talks, which were suspended after border fighting last month.

The two countries did not comply with a United Nations Security Council demand that they resume the talks by Wednesday, but Mbeki and other diplomats are nonetheless trying to get negotiations restarted.

"President Mbeki will arrive this evening in Khartoum," foreign ministry spokesman Al-Obeid Meruh told AFP.

The former South African president would meet over two days with Sudan's President Omar al-Bashir and other officials, Meruh added.

Mbeki is also expected to visit the South Sudanese capital Juba.

"He is encouraging both sides to put proposals on the table on the key issues that have divided the countries," the US government's top diplomat for Africa, Johnnie Carson, said on Wednesday.

"While there has not been a full resumption of discussions between the two sides, things are being done," Carson, assistant secretary of state for African affairs, told Africa-based reporters in a telephone news conference.

"We want them to be done much faster, and with greater alacrity and commitment."

The Security Council on May 2 gave Sudan and South Sudan two weeks to unconditionally resume negotiations. It threatened sanctions if its demands are ignored.

Following months of AU-led talks, Sudan withdrew from the process after South Sudanese troops occupied the north's main oil region of Heglig on April 10.

The 10-day seizure coincided with Sudanese air raids on South Sudanese territory, leading to fears of wider war.

The UN resolution called for a halt to the fighting and a resumption of talks to settle "critical" issues left unresolved after the South's separation in July last year following a 1983-2005 civil war.

These include oil payments, the status of each country's citizens resident in the other, the status of the contested Abyei region, and resolution of disputed and "claimed" border areas as well as demarcation of the frontier.