A strike in which both sides have accused the other of unfair labor practices has ground municipal services to a halt in Oakland for the third day in a row.

City officials say they've already made their "last, best final offer, while labor leaders from unions representing 3,000 striking city workers say the city has made "no significant movement to advance contract talks."

The labor leaders with Service Employees International Union Local 1021 and International Federation of Professional and Technical Engineers Local 21 said they're still waiting on city officials to make a "real offer to bring the parties back to the table."

City employees have been picketing at City Hall since 7 a.m. Thursday as part of a strike that started Tuesday.

So far, they've declined to move forward with a 4 percent wage increase being offered by the city, retroactively applied to July 1. That offer could also include a second 2 percent wage increase in June 2019, depending on growth in city revenue.

That offer would cost Oakland an extra $21.87 million over two years, or $22.11 million if revenue growth triggers the 2 percent wage increase in 2019, according to Oakland's Finance Department.

Oakland city officials say they're risking the creation of a $6.96 million deficit with that offer, and that measures taken to offset that deficit could aversely affect the city's credit rating.

"We cannot spend money that we do not have," Mayor Libby Schaaf said in a statement on Wednesday. "We need to consider not just the revenues we know about over the next two years, but what our financial outlook will be over the long run."

Meanwhile, labor leaders say that understaffing, high turnover and positions being left open are leading to health and safety issues for the Oakland community associated with illegal dumping as well as mandatory overtime for emergency dispatchers.

Union workers also take issue with what they describe as the overuse of part-time workers, particularly in the libraries and the Parks and Recreation Department, where they say staffers go without benefits or common worker protections against problems like sexual harassment in the workplace.

The Oakland City Council is scheduled to discuss the labor negotiations in a closed session meeting at 1 p.m. in Hearing Room 4.