I disagree, Otter. Unlike Catholicism and many Protestant denominations, Islam doesn't have a defined hierarchy. There is no "Islamic Pope" and there are no official "Islamic bishops." There is an Organization of the Islamic Conference, which consists of somewhere around 60 countries and represents about one billion of the world's Muslims but it's not an official governing body, so there simply isn't a religious leadership with the authority to declare a religious war.
There are Islamic extremist factions with leaders who call themselves "Bishop" but I don't see any difference between them and the leaders of Christian extremist factions banding together for purposes of violence. And the vast majority of Muslim leadership has vociferously denounced the terrorists.
http://www.whitehouse.gov/news/releases/2005/12/20051212.html I can't say the same for the Christian church, which sadly has been largely silent on all issues of violence.
If what you are talking about are the "shia-mullas" and ayatollahs, shia-Islam is thought to represent less than 10% of Islam. Interestingly enough, that faction is located almost entirely in Iran. As for "Al-Qaida" - that's more closely tied to the US than to any Islamic group. Al-Qaida ideology is probably most closely aligned with "Wahabism" and the greatest proponents of that ideology are Pakistan and Saudi-Arabia, who are supposed to be the strongest allies the US has in the Islamic world. Any guesses who has financed a significant portion of that teaching???