Thousands are expected to protest the governor's pension reform proposal Monday night at a rally organized by Maryland's largest union for state employees, as budget challenges return to the forefront in the General Assembly after weeks of debate on social issues.

Gov. Martin O'Malley has worked to increase collective bargaining rights in the state, which some labor leaders have said has "collective bargaining lite." There is no binding arbitration for state workers, and they do not have the right to strike. 

O'Malley, head of the Democratic Governors Association, has been highlighting his support for organized labor as a stark contrast to Republicans such as Wisconsin Gov. Scott Walker, who signed a bill to all but strip collective bargaining rights from state employees there.

"We have difficult choices ahead of us as a people," O'Malley said Friday in an interview with The Associated Press. "As one Maryland, we're going to confront those choices, and we're going to do it with dignity and respect for all stakeholders: citizens, teachers, union leaders, those that serve our citizens as elected leaders."

O'Malley is backing legislation this session to allow independent home health care providers to engage in collective bargaining activities with state agencies. Last year, O'Malley won passage of legislation granting collective bargaining rights for day care providers who contract with the state.

But Patrick Moran, director of the Maryland chapter of the American Federation of State, County and Municipal Employees, is quick to note it's the proposed changes to pensions that he expects to draw between 5,000 and 10,000 people to Annapolis, not collective bargaining concerns prompted by Wisconsin.

"It's an important issue, but it's not the issue at hand on Monday," said Moran, who directs a union representing more than 30,000 state employees.

With less than a month to go in the 90-day session, social issues such as gay marriage have dominated lawmakers' attention in recent weeks. The House on Friday returned a same-sex marriage bill to committee, effectively killing the proposal for the year.

However, another debate will begin Monday over the pension reforms.

O'Malley has proposed changes to address a troubling $19 billion in unfunded pension liabilities and $16 billion in retiree health liabilities. The plan has raised the unions' ire, partly because it would require increased contributions from state employees. The union says those workers already have suffered from three years of furloughs to help ease the state's budget problems.

Moran said the state should take other steps to deal with financial problems, such as closing a tax loophole for large businesses that operate in multiple states and reinstating a tax on people with income of more than $1 million.

While O'Malley is sympathetic to the union's objections, he said the state's current pension system is unsustainable.

"I can't blame them," O'Malley said Friday. "These aren't easy choices, but we have a couple options ahead of us. We can either address the reality of our situation together and preserve the strengths of our state and preserve the defined benefit pension system, or we can ignore the reality of our situation and have it come crashing down on the weight of its own unsustainable math."

Under the governor's plan, Maryland's funding of the system would rise from 64 percent to 80 percent by 2023.

Employees would have a choice of continuing to pay 5 percent of their salaries toward retirement with reduced benefits or increasing their contributions to retirement from 5 percent to 7 percent while earning benefits at the current level. New state employees would pay 7 percent. The proposal also includes tighter eligibility criteria, with vesting beginning at 10 years instead of 5 years. Early retirement would be increased from 55 to 60 years.

"You can't expect anybody to like these things," O'Malley said.

But Moran criticized the proposal for using money to plug budget holes, instead of directing it all to unfunded liabilities.

Monday night's "Enough is Enough" rally will be the most visible sign yet this year of union opposition.

Senate President Thomas V. Mike Miller advised his Senate colleagues last week to arrive early for a Monday evening session because of the large rally scheduled around the same time. The Senate will be debating a controversial bill to allow in-state tuition for illegal immigrants under certain circumstances, and Miller wanted to brace his colleagues for an unusually crowded night on the narrow streets of historic downtown Annapolis.

"Let me just remind you that Monday night is going to be a very confusing night," Miller told the Senate on Friday.