Abyei Area Chief Administrator complains that South Sudan government delay to resolve the status of Abyei is too much.
Ambassador Chol Deng says the implementation panel on the area is not fair, making it difficult to determine where Abyei belongs, Radio Bakhita reports.
In 2013, the people of Abyei Area voted overwhelmingly to join South Sudan in unilateral referendum.
But, South Sudan has remained indifferent over the referendum results.
Chol says it remains difficult for government and humanitarian workers to access Abyei Area.
Earlier this week, Chol called on the government to approve Abyei referendum results in the parliament for it to be recognised internationally.
But, there is no response from the government.
The Transitional National Legislative Assembly provided for in August 2015 Peace Agreement has not been established yet.