By Ray Sanchez

NEW YORK (Reuters) - Protesters who have camped out near Wall Street for two weeks were preparing on Friday to march to police headquarters over what they viewed as excessive force and unfair treatment of minorities and Muslims.

The Occupy Wall Street movement, whose members have vowed to stay through the winter, have been protesting an array of issues including the 2008 bank bailouts, foreclosures and high unemployment.

About 500 people were gathered ahead of the start of the late afternoon march to One Police Plaza, the center of police operations, in downtown Manhattan.

Online flyers for Friday's march say "No to Stop-and-Frisk in Black & Latino neighborhoods" and "No to Spying and Harassment of Muslim Communities."

The protest encampment in Zuccotti Park in downtown Manhattan is festooned with placards and anti-Wall Street slogans. There is a makeshift kitchen and library, and celebrities from filmmaker Michael Moore to actress Susan Sarandon have stopped by to show solidarity.

Asked on his weekly radio show on Friday whether the protesters could stay indefinitely at the private park they call their base, Mayor Michael Bloomberg said, "We'll see."

Bloomberg added: "People have a right to protest but we also have to make sure that people who don't want to protest can go down the street unmolested."

The demonstration comes less than a week after police arrested 80 people during a march to the bustling Union Square shopping district, the most arrests from a demonstration since hundreds were detained outside the Republican National Convention in 2004.

A police commander used pepper spray on four women at that march, and a video of the incident went viral on the Internet, angering many protesters who vowed to continue their protests indefinitely.

Police have said pepper spray was a better alternative than night sticks to subdue those blocking traffic.

While the protest has been made up mostly of young people, it also has recently attracted the support of a loose coalition of labor and community organizations.

Among those pledging solidarity were the United Federation of Teachers and the Transport Workers Union Local 100, which has 38,000 members. The unions could provide important organizational and financial support for the largely leaderless movement.

Similar protests are sprouting in other cities, including Boston, Chicago and San Francisco.

(Editing by Ellen Wulfhorst and Cynthia Johnston)