Several other US Muslim leaders expressed similar concerns about the pope, but pledged to participate in the Washington gathering, saying the two faiths should do everything possible to improve relations.

"Our going there is more out of respect for the Catholic Church itself," said Muzammil H Siddiqi, chairman of the Fiqh Council of North America, which interprets Islamic law. "Popes come and go, but the church is there."

Siddiqi, co-chairman of the West Coast Muslim-Catholic Dialogue, is among the Muslim, Jewish, Buddhist, Jain and Hindu leaders scheduled to meet Benedict on Thursday at the Pope John Paul II Cultural Center. Muslims and Roman Catholics each have more than 1 billion followers worldwide. US Catholic and Muslim leaders started holding interfaith talks in the early 1990s, and many of the Muslim leaders invited to the event Thursday are veterans of those discussions.

But Salam al-Marayati, executive director of the Muslim Public Affairs Council, and advocacy group based in Los Angeles, said the event seemed "more ceremonial than sustantive" and his organization would not participate. He said he was disappointed that no time was made in the pope's six-day trip or even a brief private meeting with US Muslim leaders.