The Pew study found that six in 10 U.S.-born Muslims faulted Islamic leaders for not speaking out against extremism, as did 43 percent of Muslim immigrants.

Officials with Muslim advocacy groups say that they have spoken out repeatedly against extremists but that the American public, including Muslims, often doesn’t hear about it.

“Our reach in terms of community awareness of our programs promoting moderation is not where we’d like it to be,” said Safaa Zarzour, secretary general of the Islamic Society of North America, the nation’s largest Muslim group.

Zarzour said that anti-Muslim sentiment in the United States is concentrated among a few individuals and groups. Most Muslims have warm relations with colleagues, neighbors and local public officials, he said.