"They need to be more serious in their role as mediators between us and the Israelis," Abbas told reporters in Tunis, where he arrived on Thursday for an official visit. The Palestinians "will continue their efforts to attain full UN membership", he said, adding that he was due to meet a senior US official on Saturday. Israel's top US ally has vowed to veto any UN vote on full Palestinian membership but Abbas scored a symbolic victory last month when the Palestinians were admitted as a member of UNESCO, the United Nations' cultural agency. Abbas now eyes membership of more world bodies such as the UN Framework Convention on Climate Change. The United States and Israel oppose Palestinian membership of the United Nations because they say there must be direct Palestinian-Israel talks on setting up a new state.