Israeli Prime Minister Ariel Sharon has pledged to block the release of a Palestinian militant leader currently being held in international custody in the West Bank. He was speaking after the Palestinian Authority's High Court ordered the immediate release of Ahmed Saadat, leader of the Popular Front for the Liberation of Palestine (PFLP). Israel, which wants to arrest Mr Saadat in connection with the assassination of a cabinet minister last October, agreed in April to have him placed in the custody of US and British prison guards in the West Bank. The row erupted on the same day the director of the US Central Intelligence Agency (CIA), George Tenet, arrived in Israel to press for reform in the Palestinian Authority.