At least 2,000 members of a union representing office janitorial workers marched through downtown Newark this afternoon following a vote authorizing a strike if a deal can’t be struck by Jan. 1, 2012, when their current contract expires.

Members of Local 32 BJ of the Service Employees International Union blew whistles and pounded on makeshift drums as they marched down Market Street to Broad Street, then to Military Park, where a brief rally was held shortly after 5 pm. The marchers, clad in purple and gold, were escorted by Newark police.

Shortly before the march, members from 10 counties across New Jersey gathered at Essex County College for a vote to authorize the strike. That vote was “unanimous” in favor, said Kevin Brown, the union’s state director. The union has offices in Newark and New York City.

At issue is a proposed 15-month wage freeze coupled with an increase in medical costs, said Maia Davis, a union spokeswoman.

“Many of these people only make $12 an hour. Many of our members work two and three jobs,” Davis told Patch this afternoon. “They’re …. effectively asking them to take a pay cut.”

Speaking in Spanish with an interpreter, Dinora Alberto, who like many of the union’s members is an immigrant, said the concessions would be a tremendous burden for her.

“It would affect us very much because I’m the only one providing for my family economically,” said Alberto, the single mother of an 8-year-old daughter.

The workers are employed by a few large janitorial services firms, including American Building Maintenance, Allan Industries and CRS Facilities Services. Numbering about 7,000, they work in 400 office buildings, including facilities along the Hudson River waterfront and in Newark. The buildings are owned by companies -- including Prudential of Newark --  which hire the janitorial firms.

Local 32BJ has been in negotiations with a consortium representing the janitorial firms since Oct. 18, the union said in a statement.

A contact number for that consortium could not immediately be obtained. A call placed to American Building Maintenance was not immediately returned.