Thousands of union members rallied on Independence Mall Saturday morning, calling on Mayor Nutter to negotiate with some of the city's largest unions, who have gone without a contract for four years.

National labor leaders, including the president of the American Federation of State, County and Municipal Employees and the head of the American Federation of Teachers, rallied a crowd of nearly 2,000 for two hours Saturday morning.

"In the United States, we tell our kids, you have to go to college," said Randi Weingarten, the president of the American Federation of Teachers. "In Philadelphia we take away the things kids need to have access to go to college."

She was referring to the announcement of 37 public school closings in the city, unveiled in December as a cost-cutting measure.

Rally organizers said the event was designed to honor Dr. Martin Luther King, Jr., and several speakers quoted him in their speeches. Many noted that King was killed while supporting AFCSME-affiliated sanitation workers in Memphis.

The city presented a "final offer" to AFSCME's District 33, which represents Philadelphia's non-uniformed municipal workers, earlier this week. The union rejected that offer, which included reduced pensions and furlough authority.

Mayoral spokesman Mark McDonald called that offer "a bit of a watershed" and said Mayor Nutter felt that furloughs were a better alternative to layoffs.

"The mayor ran on a platform in 2007 that he would reform the pension system in the city, would reform health care and would create an environment where there are work rules for city employees that are essentially sustainable, that city taxpayers can afford," he said.

Nutter has offered the AFSCME local pay raises but the union has rejected the deal because it includes furloughs and the raises are not retroactive to 2009 when the contract expired.

Contract Aubrey Whelan at 215-854-2771 or or follow on Twitter at @aubreyjwhelan