OAKLAND (CBS SF) — Union leaders representing more than 3,000 Oakland city employees said Monday that the workers will go on an indefinite strike on Tuesday to protest what they allege are the city’s unfair labor practices.

Leaders of Service Employees International Union Local 1021 and International Federation of Professional and Technical Engineers said they offered to enter informal, pre-impasse mediation with the help of former San Francisco Mayor and California Assembly Speaker Willie Brown but the city refused their offer.

“Nobody wants to see a strike, but we have gotten to a point where we don’t really have a choice,” said union employee Waliana Dieu said Monday.

Oakland city spokeswoman Karen Boyd and a spokesman for Oakland Mayor Libby Schaaf didn’t immediately respond to a request for comment on the unions’ statement that they will go on strike because the city rejected their mediation offer.

In a statement on Friday night, the city said, “Due to significant staff shortages, a strike will force the city to close nearly every city facility starting on Tuesday morning.”

The city released a full list of the services and facilities that would be affected by the strike.

City of Oakland officials alleged late Monday afternoon that the strike planned by city employees is unlawful because the parties have not reached an impasse.

The city said in a statement, “Under California law, both the City and its labor unions have a duty to bargain and to participate in statutory impasse procedures in good faith. The city cannot unilaterally implement concessions and the unions cannot strike until the completion of those processes, including fact-finding.”

City officials said, “The parties are not at impasse, and the city has not yet had an opportunity to present the union’s latest proposal to the City Council for consideration. The City Council is scheduled to meet on Wednesday, which was the soonest legally possible.”

However, the city said sworn police and fire personnel won’t participate in a strike since they are represented by other unions.

Earlier Monday, SEIU Local 1021 chief negotiator Rob Szykowny said Local 1021 and other unions that represent city employees would be willing to postpone a strike if the city agrees to give workers a 4 percent pay increase for one year and continue talking about an agreement for two additional years with Brown acting as a mediator.

Schaaf didn’t comment on the possibility of a one-year deal and working with Brown as a mediator earlier Monday, but issued a statement in which she said, “We will continue to work hard to avert a strike.”

“We value our city employees and there is no doubt our workers deserve increased compensation. Yet the City of Oakland cannot offer more than it can afford, and it cannot come at the expense of the services we provide,” Schaaf said.

She said, “All city employees and residents deserve a financially stable and sustainable Oakland.”

Szykowny said if employees go on strike, it would be because of what he described as “multiple unfair labor practices” by the city, workplace conditions, understaffing levels and cost of living concerns.

Szykowny said SEIU Local 1021 and other unions have been negotiating with the city for seven months but haven’t been able to reach an agreement yet.

Local 1021 represents more than 2,000 public works employees, parking enforcement officers, Head Start instructors, and early education teachers.

Local 1021 spokesman Chris Flink said if that union goes on strike, IFPTE Local 21, which represents about 1,000 professional and technical employees, including engineers, building inspectors and planners, would engage in a sympathy strike.

In addition, several hundred city employees who belong to the International Brotherhood of Electrical Workers would respect Local 1021’s picket lines, according to Flink.

Oakland city officials said in the statement they issued on Friday night that they made a “last, best and final offer” that includes wage increases of up to 6 percent over three years, including 4 percent for the first year of their proposed contract.

The city said it also will continue to provide fully-paid family health care benefits and absorb all pension and health care-related rate increases.

SEIU Local 1021 conducted a half-day strike on Nov. 2 that shut down Oakland libraries, senior centers, child care programs, park and recreation centers and other city services.

Oakland workers will be striking starting at 7 a.m. Tuesday. Picket lines will be up throughout the city, including the Equipment Services Facility at 7101 Edgewater Drive at Oakland City Hall.

The sanctioned strike also will be held in front of Mayor Libby Schaaf’s re-election fundraiser hosted by Oakland’s top developers and property owners.

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