(Repeats story from Thursday without changes) * Fight against Islamic State is a long haul * U.S.-led effort requires local forces on the ground * Fight in Syria complicated by Assad in power * Militants may target "west's soft underbelly" * Saudi-Iran detente could pave way for a deal on Syria By Samia Nakhoul BEIRUT, Sept 25 (Reuters) - American-led and Arab-backed air strikes carrying the fight against Islamic State from Iraq into Syria have dragged Washington into a new Middle East war - exactly the kind of conflict Barack Obama spent his presidency trying to avoid. ...