March 5 (Bloomberg) — A group of California mayors is opposing a pension-reform referendum that would empower them to reduce expenses while risking their support from unions.

The statewide measure, offered by San Jose Mayor Chuck Reed, would give local officials authority to reduce future pension benefits for municipal employees. Current and former mayors representing 17 California cities are among leaders who oppose his proposal, while three mayors favor it. The measure probably won't make it onto the ballot this November because Reed is suing the state over the wording of its summary.

"Public-sector unions are very powerful, very influential and generally say 'no' to any kind of changes," Reed, a 65- year-old Democrat, said in a telephone interview. "It's impossible to get elected to statewide office unless you have union support."