The Oakland City Council voted Thursday to lay off 80 of the Police Department's 776 officers as it slashed at a $30.5 million budget deficit. The decision could be rescinded if the police union agrees to pension concessions.

Council members would like the officers to contribute 9 percent of their salaries toward their CalPERS pension, the same as every other city union worker.

Union leaders and city officials are set to negotiate Sunday and Monday, a move some interpreted as a sign the union was willing to change its position.

"I'm confident that we can have an agreement by July 15," said Councilwoman Jean Quan, who voted for the measure, which passed 5-3. "No one cancels their weekend unless they plan to negotiate."

Sgt. Dom Arotzarena, the union president, would only say, "It's not over yet."

The union was under relentless attack all night from council members and a wide range of speakers, who called it a matter of fairness that the police union be treated like the other city unions.

"Police unions needs cuts too!" said a sign held by Lydia Kosmos, 20, a lifelong Oakland resident who works at the Montclair Recreation Center.

"Quite frankly, our pension program that allows any employee to retire at $100,000 a year at age 50 is unsustainable," Quan said.

But police union officials see it differently.

They see a city that squandered money in good times and now is coming to employees to make up the difference. Firefighters pay into their pensions, but they were given a salary increase to make up the difference, Arotzarena said.

If police do not agree to the pension request, the council's layoff plan Thursday is a gamble.

It assumes that voters will pass a ballot measure in November that will suspend for three years a mandate that the Police Department have 739 officers. Without that suspension, the city will lose $20 million a year in police funding from a parcel tax that voters approved in 2004.

If the measure passes, an additional 27 officers would have to be laid off Jan. 1.

The council is also considering a parcel tax that would cost each single-family home about $360 and bring in about $50 million.

If the parcel tax and the minimum staffing measures both fail, the city would be forced to lay off 202 officers by Jan. 1.

Oakland has been reconciling itself to the worst economy in 70 years.

Like other cities around the state, Oakland's property, sales and property transfer tax revenues have dried up during the Great Recession. The city's $407 million budget represents a revenue decline of $69 million in just five years.

At the same time, the city has been treating police and fire budgets as all but sacrosanct. As other city departments have been steadily whittled back, Oakland's budget has been increasingly dominated by public safety expenses.

In 2005-06, police and fire accounted for 61 percent of the budget, according to City Administrator Dan Lindheim. For 2010-11, they will account for 75 percent.

Debt payments account for another 11 percent of the budget, and voter-mandated spending for children's programs and libraries ties up 6 percent. That leaves just $25 million in discretionary spending - or $5.5 million less than the deficit that needs to be eliminated.

"There's just very little left to cut," Lindheim said.

Firefighters have a no-layoff clause in their contract, so council members and Mayor Ron Dellums have said they have no choice but to lay off police. However, they also have promised to hold off for at least five months - until ballot measures to boost police funding can be brought before voters - if officers agree to concessions on their pensions.

The Oakland Police Officers Association is seeking at least a two-year guarantee of no layoffs in return for pension concessions, something the council has been unwilling to do because future years have greater deficits.

"We have to look at the next five years and put this city in a position where we start correcting this incredible structural deficit," said Councilman Ignacio De La Fuente, a longtime labor leader.