SAN MARCOS -- Representatives from the San Marcos Firefighters Association and Deputy Sheriffs Association of San Diego County said in a news conference Friday that Proposition O threatens some public services in the city.

Put on the ballot by residents, the growth-control initiative would require voter approval for most development projects that do not conform to the city's general plan -- a blueprint for future growth. Prop. O needs a majority of votes on Nov. 4 to pass.

The firefighters and deputies associations previously came out against the initiative.

On Friday, a dozen firefighters, deputies and members of a political action committee were on hand to support firefighters association President Mike Korby as he described the city's fire department as first-rate.

He said the agency functions well because of money the city receives from sales and property tax as well as developers.

That funding will come to a halt and future road and traffic improvements will be at stake if Prop. O passes, said Korby.

"If our funds are cut, it would threaten our ability to provide the high level of service residents expect from us," Korby said. "If you block traffic improvements, you decrease our response times. There would be more traffic congestion under Prop. O."

Cynthia Skovgard, who is leading the campaign to get Prop. O passed, said Friday that the opposite is true.

"We're going to be underfunded if we keep on going with out-of-control growth," she said. "That's why we're doing this. We don't want to lose the quality that we have now."

Skovgard and other Prop. O supporters said the measure is needed to stop the City Council from approving large developments that residents do not want.

Opponents, including all five City Council members, have pointed out that the city's general plan was created decades ago, long before existing developments such as Cal State San Marcos and the massive San Elijo Hills residential neighborhood were envisioned.

Deputy sheriffs association President Ernie Carrillo said that if Prop. O passes, the city will lose an estimated $500,000 in potential developers fees and sales taxes, referring to concerns that developers won't want to go through the time, expense and uncertainty of an election.

Contact staff writer Andrea Moss at (760) 739-6654 or amoss@nctimes.com.