Johannesburg — The “troublesome, problematic” issue of whether the Abyei region belongs in South Sudan or Sudan is the most important issue still to be resolved between the two countries, says African Union mediator Thabo Mbeki.

Addressing a church meeting in Benoni, near Johannesburg, on Thursday, Mbeki was upbeat about progress in bringing about peace between the Sudans since the south became independent in 2011.

Both Khartoum and Juba are in practice implementing the range of nine agreements they signed a year ago, he said.

“Whereas all of us were very fearful that the countries could slip back into a civil war, now there's a very strong sense that both countries are moving further and further away from that possibility.”

But the future of Abyei is “one big matter that has not been resolved.” The people of the region are scheduled to decide in a referendum which country they want to be part of.

Mbeki said the Ngok Dinka people, who claimed the area historically – “and nobody disputes that” – could be expected to vote in the referendum to join South Sudan. But the Misseriya people – “who are called an Arab tribe” – also said the area belonged to them.

“I'm sure that all of us know this very well,” said Mbeki, “that once any... one in our countries gets described, characterised, caught up in these is tribal, ethnic identifies then it becomes difficult to solve.”

But the AU panel was continuing to engage both governments: “It's troublesome, problematic, it's got its own dynamics which make it difficult for both sides to move.”

Mbeki was speaking to the provincial synod of the Anglican Church of Southern Africa, which had as a guest Archbishop Daniel Deng Bul, the leader of the Episcopal Church of the Sudan.