He added: “The average American just thinks this is a political statement. It’s not about religion, and is clearly an aggressive act that is offensive.”

Several family members of victims at the World Trade Center have weighed in against the plan, saying it would desecrate what amounts to a graveyard. “When I look over there and see a mosque, it’s going to hurt,” C. Lee Hanson, whose son, Peter, was killed in the attacks, said at a recent public hearing. “Build it someplace else.”

Those who support it seem mystified and flustered by the heated opposition. They contend that the project, with an estimated cost of $100 million, is intended to span the divide between Muslim and non-Muslim, not widen it.

Oz Sultan, the programming director for the center, said the complex was based on Jewish community centers and Y.M.C.A.’s in Manhattan. It is to have a board composed of Muslim, Christian and Jewish leaders and is intended to create a national model of moderate Islam.

“We are looking to build bridges between faiths,” Mr. Sultan said in an interview.

City officials, particularly Mayor Michael R. Bloomberg, have forcefully defended the project on the grounds of religious freedom, saying that government has no place dictating where a house of worship is located. The local community board has given overwhelming backing to the project, and the city’s landmarks commission is expected to do the same on Tuesday.

“What is great about America, and particularly New York, is we welcome everybody, and if we are so afraid of something like this, what does that say about us?” Mr. Bloomberg asked recently.

“Democracy is stronger than this,” he added. “And for us to just say no is just, I think  not appropriate is a nice way to phrase it.”