Many Muslims believe that the Brotherhood is a noble international movement that supports the true teachings of Islam and unwaveringly defends Muslims who have come under attack around the world, from Chechens to Palestinians to Iraqis. But others view it as an extreme organization that breeds intolerance and militancy.
"They have this idea that Muslims come first, not that humans come first," says Mustafa Saied, 32, a Floridian who left the U.S. Brotherhood in 1998.
While separation of church and state is a bedrock principle of American democracy, the international Brotherhood preaches that religion and politics cannot be separated and that governments eventually should be Islamic. The group also champions martyrdom and jihad, or holy war, as a means of self-defense and has provided the philosophical underpinnings for Muslim militants worldwide.
Many moderate Muslims in America are uncomfortable with the views preached at mosques influenced by the Brotherhood, scholars say. Those experts point to a 2001 study sponsored by four Muslim advocacy and religious groups that found that only a third of U.S. Muslims attend mosques.