NEW YORK (CBSNewYork) — Thousands of unionized New York City office cleaners hit the streets Wednesday afternoon to demand a fair contract.

Members of the 32BJ Service Employees International Union began marching from 41st Street and Sixth Avenue at 3 p.m. to 48th Street, where they rallied.

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“This is really a fight for the middle class.  Everybody out here is somebody that works hard every day, goes to work at 4 o’clock, gets off at 1 o’clock in the morning,” said Mike Fishman, the president of the union.

The union is fighting against a proposal to create a two-tier wage and benefit system and fighting for wage increases.  The workers have also authorized a strike if no contract deal can be reached with the Realty Advisory Board.

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The current contract expires at the end of the month.

A strike could potentially affect 1,500 commercial office buildings in the city including Rockefeller Center, the Met Life Building, the Empire State Building and the Time-Warner Center.

The union said the highest rate for its cleaners is $22.65 per hour, which amounts to about $47,000 annually.  That is a number that the union says is “significantly less than the household income that independent researchers have shown is necessary to support a family of four.”

However, management has said the city’s cleaning workers are the highest paid in the country.