CALIFORNIA - Union leaders for Muni drivers reached a tentative deal late Friday with Mayor Gavin Newsom's administration that could prevent price increases in monthly passes for seniors, youth and the disabled and reduce systemwide service cuts, The Chronicle has learned.

Both sides declined to discuss specifics, but during four days of intense negotiations, the talks focused on cost savings from having drivers start contributing to their retirement accounts and unspecified work rule changes.

The estimated savings will be $14.9 million over two years. The savings would help reduce service cuts from 10 percent to about 6.5 percent, reduce the number of drivers that will be laid off and possibly eliminate the need to extend metered parking to Sundays. However, Sunday parking could be brought back as a way to generate new revenue for the next budget cycle, which begins July 1.

The changes will help the agency bridge a $16.9 million budget gap for this year and could help address an even bigger shortfall for next year, which is now projected to be $52.7 million.

Muni, like most transit agencies in the state, has been hit hard by the elimination of state transit funding and the economy. In addition, the city has reduced its general fund contribution to the agency, which raised fares and cut service last year.

The efforts to balance the current fiscal budget, which ends June 30, and the next year's budget, could result in some of the deepest service cuts in the agency's history. While last year's service reductions were targeted to routes with fewer riders, the new cuts would be implemented on all Muni routes.