South Sudan insists a controversial referendum on Abyei must be held this month. But observers say the vote is unlikely to go ahead. South Sudan has failed to reach a deal with neighbouring Sudan over who should be eligible to vote, despite efforts by African Union mediator Thabo Mbeki. The dispute focuses on Misseriya nomads. Khartoum believes these herders should be allowed to vote but Juba disagrees. Misseriya tribal leader Sadig Babo Nimir comments.