The city of Philadelphia has made what it calls a "final offer" to the blue-collar workers union District Council 33.

The offer has no provision for salary increases over the years that the union has been on the job without an agreement.

It also calls for big pension changes and other concessions.

The union rejected the offer at the most recent negotiating session.

Mayor Michael Nutter would not say city officials are ready to impose a contract on District Council 33, which has been without a contract since 2009, instead saying the city will act if an agreement isn't reached in two weeks.

"It's fundamentally unfair to both our hardworking dedicated and committed public employees who have gone without a pay raise for years now, as well as our taxpayers, if we don't take affirmative action to put our very fair offer into effect," Nutter said Wednesday.

The offer includes raises that would begin after ratification of the contract, not for the years the union worked without a contract.  It also calls for pension concessions, possible furlough days and other work-rule changes. City officials say the workers will come out slightly ahead because of other elements of the deal.

Chief negotiator Shannon Farmer says with the two-week window the mayor has offered, it's up to the union now.

"The ball is in the union's court on whether they want to meet in that time period. We believe the negotiations are at an impasse, but we will be meeting if the union feels there is a benefit of doing so," Farmer said Wednesday.

Farmer says the union rejected the offer at the most recent negotiating session, saying it wants raises for every year of the contract.

"District Council 33 simply cannot be permitted to hold the citizens of this great city hostage any longer," Farmer wrote in a letter to the union.

The city has not yet made a final offer to the white-collar workers represented by District Council 47.