|Officals have warned that Sudan could return to confict if the Abyei impasse is not resolved [EPA]
The latest round of talks between north and south Sudan over the future of the oil-producing Abyei region has failed to reach an agreement.
The issue stands as a key hurdle ahead of referendums in the country, and according to the north's National Congress party (NCP) and the south's ruling Sudan People's Liberation Movement (SPLM), "serious efforts and many productive discussions, [the delegations] did not succeed in reaching agreement on the eligibility criteria for voters in the Abyei Area referendum".
The NCP and SPLM also said in a joint statement on Tuesday that both parties "will meet again in Ethiopia toward the end of October to continue their discussions. The parties continue to commit themselves to their mutual goal of avoiding a return to conflict".
Local residents in Abyei will vote on whether the region should join north or south Sudan in a plebiscite scheduled for early next year, which was promised as part of the 2005 peace deal that ended decades of north-south civil war.
The vote is set to be held alongside south Sudan's referendum on independence from the north.
'Time is critical'
However, the head of the southern delegation warned the country could return to war if a deal is not reached.
"This round has failed," Pagan Amum, secretary-general of the SPLM, told reporters in the Ethiopian capital Addis Ababa where the talks were held.
"We are left with 90 days. The time is very critical. If the parties fail to sort out these issues this could lead to an end of the peace process itself. And the peace may unravel in Sudan."
Delegates at the meeting also told the Reuters news agency that Ali Osman Taha, Sudan's second vice-president was flying to Juba on Tuesday to meet Salva Kiir, the south Sudan president, who is also a vice-president in Sudan's national power-sharing government, in an attempt to salvage the talks.
An observer at the talks, who declined to be identified, reported that Thabo Mbeki, the former South African president, had offered to mediate when talks resumed.
Hillary Clinton, the US secretary of state, had urged the government in Khartoum to come to the talks prepared to negotiate.
Delegates in Addis Ababa told Reuters one possible solution to the impasse was to forego the referendum on Abyei and divide its territory between the north and the south.
However, the teams were unable to agree on any possible border demarcation and what would qualify as Abyei citizenship.
The SPLM says the northern government is settling thousands of Missiriya, a tribe from central Sudan, in northern Abyei to influence the vote. The Khartoum government denies this.
In a sign of mounting tension, south Sudan's army told Reuters news agency that four northern soldiers walked into the centre of Abyei town on Monday evening and started shooting randomly in the air, slightly injuring a local resident.
Along with the Abyei plebiscite, there will also be a referendum on whether south Sudan should secede from the north.
That vote is widely expected to result in the creation of Africa's newest country, a development opposed by Khartoum.