RAMALLAH, West Bank - President Mahmoud Abbas said he hoped talks between Palestinian factions to begin Sunday would resolve critical disagreements and make his plan to call a referendum recognizing Israel's right to exist unnecessary. The Palestinian government has been internationally isolated and is suffering a crippling economic boycott since the Islamic militant group Hamas won Jan. 25 parliamentary elections. The United States and European Union have demanded Hamas renounce violence and recognize Israel's right to exist if it wants the aid restored. Hamas has refused. In a bold move intended to force Hamas to moderate its position, Abbas, who...