The city's police and fire unions have called off a protest of the U.S. Conference of Mayors that will begin in Baltimore later this week.

"It's about messaging getting for our members what they deserve," said Fraternal Order of Police president Bob Cherry. "We thought going back to a billboard reminding mayors of the importance of public safety was the best way to go."

Speakers at the conference, which begins Thursday night and runs through Monday, include House of Representatives Democratic leader Nancy Pelosi, HUD Secretary Shaun Donovan and U.S. Department of Health and Human Services Secretary Kathleen Sebelius. About 200 mayors and their staff are expected to be in the city through Monday morning.

Gov. Martin O'Malley and filmmaker John Waters are slated to entertain the mayors.

The unions had threatened last winter to picket the conference to push Mayor Stephanie Rawlings-Blake to compromise over furlough days and pension benefits. The police and firefighters union remain locked in a legal battle with the city over changes to their pension plan that Rawlings-Blake pushed through last year.

Cherry declined to describe the message to be printed on the billboard. Last year, the unions posted a billboard near City Hall that said, "Welcome to Baltimore, Home to a Mayor & City Council who turned their backs on our Police & Firefighters."