JERUSALEM, May 15 (Xinhua) -- Visiting U.S. President George W.Bush on Thursday said in an address delivered to Israeli Knesset (parliament) that the world must not allow Iran to have a nuclear weapon.

　　"Permitting the world's leading sponsor of terror to possess the world's deadliest weapon would be an unforgivable betrayal of future generations," the U.S. president said, adding that for the sake of peace, the world must not allow Iran to have a nuclear weapon.

　　Bush blamed Hamas, Hezbollah, Iran for their stances on Israel,saying the fight against terror is the defining challenge of the time, a great ideological struggle. He said they will be defeated."We believe that religious liberty is fundamental to civilized society so we condemn anti-Semitism in all forms whether by those who openly question Israel's right to exist, or by others who quietly excuse them," Bush said.

　　He said America is proud to be Israel's closest ally and best friend in the world.

　　Bush is in Israel for a three-day visit to mark the Jewish state's 60th anniversary of its independence.