The nonprofit group Park51 said Feisal Abdul Rauf, who is set to start a national speaking tour Saturday and spends much of his time out of the country, didn't have enough time to spend on the center.
The group announced it had named a new senior adviser to help lead religious programing: Shaykh Abdallah Adhami, a scholar with an architecture degree known for his lectures on gender relations.
Rauf, who helped come up with the idea for the center, and later promoted it amid fierce controversy over its location, announced late this fall that he would be starting a global movement that would fight extremism and promote better relations between people of different faiths and cultures.
Rauf will remain on the Islamic center's board and involved in the project, Park51 said in a statement. But the group said it needed someone who could be more focused on the day-to-day business of building a local congregation.
"Due to the fact that Imam Feisal is focusing most of his energies and passion on launching this new and separate initiative, it is important that the needs of Park51, the Islamic community center in lower Manhattan, take precedence," the statement said.
The group said that while Rauf's vision is "truly exceptional, our community in lower Manhattan is local. Our focus is and must remain the residents of lower Manhattan and the Muslim American community in the greater New York area."
A spokeswoman for Rauf had no immediate comment Friday on the announcement.
The backers of the community center and mosque are planning on replacing a defunct clothing store two blocks from ground zero with a 13- to 16-story building that would hold athletic facilities, a day care center, art galleries, an auditorium for cultural events, a Sept. 11 memorial and a prayer space with room for a congregation of about 1,000.
Critics have assailed the project as insensitive, saying it is improper for a Muslim institution to be located so close to the site of an attack by Islamic extremists.
Rauf's global travels have been a problem for the project before. He left for a long, State Department-funded trip to the Middle East just as the frenzy over the mosque was exploding at home.
He stayed silent for weeks as criticism mounted, leaving mostly his wife, the community activist Daisy Khan, to respond.
Park51, which is controlled by the Manhattan real estate investor who owns the site of the planned center, Sharif El-Gamal, said Adhami would be one of several imams who would eventually be picked to coordinate religious services in the building.
Adhami has already performed guest lectures at the site of the planned center. One of his appearances there came in August, at the height of media coverage of the project.
At the time, Adhami seemed to take the crush of attention with nonchalance. His representatives invited reporters to cover his speech, only to have El-Gamal, who was unaware of the invitation, toss them out after they arrived. Adhami shrugged it off afterward as a misunderstanding and calmly fielded questions.
In a statement released by a Park51 publicist Friday, Adhami said he was being given "an extraordinary opportunity to be a key adviser on a project going forward that has enormous creative and healing potential for the collective good in New York City and in our nation."
Everyone associated with the project has had to endure intense, sometimes savage scrutiny, and Adhami is likely to be no different.
Born in Washington, D.C., he began his religious education as a child in Syria, and later earned an architecture degree from the Pratt Institute in Brooklyn. He now lectures widely on issues of religious law, family and sexuality.