Amid warnings of another al Qaeda attack on the United States, American Muslims have launched a public relations campaign stressing that they condemn terrorism and should not be blamed for violence committed in the name of Islam.

The loosely coordinated campaign by Muslim organizations includes newspaper advertisements, a petition drive and public commitments to work hand in hand with law enforcement agencies, including a joint effort to begin today with FBI Director Robert S. Mueller III.

"We want to debunk the myth that American Muslims are not concerned with securing our homeland," said Salam Al-Marayati, executive director of the Muslim Public Affairs Council, which will announce a "grass-roots Muslim initiative against terrorism" with Mueller at a Los Angeles mosque. Al-Marayati said the council will work with the FBI to denounce terrorism, control "belligerence" at mosques and improve communication between Muslims and U.S. law enforcement agencies.

Other national Muslim organizations are engaged in similar efforts. In the past two weeks, individuals and groups representing more than 500,000 U.S. Muslims have signed a petition against terrorism on the Web site of the Washington-based Council on American-Islamic Relations, according to CAIR spokesman Ibrahim Hooper. "No injustice done to Muslims can ever justify the massacre of innocent people, and no act of terror will ever serve the cause of Islam," the online petition states.

On Wednesday, CAIR also published a full-page advertisement in the Los Angeles Times titled "No to terrorism, No to bigotry." Citing the online petition, it said: "American Muslims condemn all acts of terrorism and are outraged as their fellow Americans by atrocities committed in the name of God and their faith."

Hussam Ayloush, head of CAIR's Southern California office, declined to reveal the cost of the ad but said five Los Angeles-area Muslim businessmen paid for it. Fundraising for similar advertisements is underway in other cities, including New York, Houston and St. Louis, he said.

In Northern Virginia, Kamal Nawash, a lawyer and Palestinian immigrant, began the Free Muslim Coalition Against Terrorism last week to oppose Islamic extremism, whose supporters in the Middle East, he said, are "growing by the day."

Nawash said he believes that most American Muslim organizations are not forceful enough in condemning terrorism. "There has not been a voice that unconditionally opposes terrorism by any mainstream Muslim organization in this country," he said.

But Hooper said every major Muslim group in the nation signed a joint statement against terrorism after the Sept. 11, 2001, attacks on the Pentagon and World Trade Center.

"Unfortunately, the most frequent criticism that's tossed at the American Muslim community is, 'You never denounce terrorism,' ignoring the fact that we've denounced terrorism every which way from Sunday," he said. "I don't know what more we can do, and that is part of why we launched these initiatives."