Saeb Erekat is the chief negotiator for the PLO Steering and Monitoring Committee, not the PA. Indeed, as far as I know he holds no official position **whatsoever** within the PA government of Fayyad. The negotiations on end-of-status is a matter of "national liberation", and that means it is a matter between the "Govt of the State" and the "National Liberation Movement". And that means it is between "The Govt of Israel" vs. "The PLO". It has been thus since 1993, and it has not changed in all the long years post-Oslo.
Islamist militants attack African Union base in southern Somalia (Reuters)
from the article: PA: Place supervisors in settlements to ensure freeze