Senior US diplomat Frederic Hof landed in Damascus Friday Oct. 8, with a strong ultimatum from US President Barack Obama warning Syrian President Bashar Assad that he would be held personally responsible for any military action Hizballah may pursue in Beirut or any other part of Lebanon. Such action would have consequences for the Syrian ruler's standing in Washington and that of his country. This is revealed byDEBKAfile's sources in Washington and Beirut.