BEIRUT (Reuters) - Hezbollah leader Sayyed Hassan Nasrallah said on Friday an Israeli war with Lebanon was unlikely and warned Israel against exploiting the current political crisis in Lebanon.     Lebanese Prime Minister Saad al-Hariri resigned in a speech from Saudi Arabia on Saturday and has yet to return to Lebanon. In a televised address Nasrallah said he believes Hariri is being detained in Riyadh.   