Sonoma County government's largest labor union voted Tuesday by a slim 52 percent majority to approve a proposed labor contract that would balance a short-term salary freeze with future-year wage growth.

But because not all six county bargaining units in Service Employees International Union Local 1021 concurred in the ratification vote, union officials were unclear about its legal outcome.

Lathe Gill, the union's Santa Rosa-based area director, said officials would be reviewing the result with attorneys, a process he said could take "a few days."

The uncertainty has to do with whether the union follows past practice, which required majority approval by all bargaining units, or whether an overall majority is enough to ratify the contract, as dictated by current union bylaws, Gill said.

"The vote was close enough that that is in question," he said.

He added that any final determination was likely to face an internal challenge within the union, a sign of how contested negotiations have been with the 1,700-member organization, representing nearly half of all county employees.

About three-quarters of the 1,200 SEIU members eligible to vote participated in the election, Gill said.

Jim Leddy, a county spokesman, said the county was pleased to hear about the majority vote Tuesday night. But he said county officials were awaiting word from the union before offering any additional comment.

The muddled result leaves talks between the two sides in limbo. Approval of the agreement could defuse what has been an escalating legal fight between the union and the county. Rejection, however, would set the stage for an even more protracted battle, including a likely strike.

Tuesday's vote was the second by the union after 11 months of protracted negotiations. In the previous vote, in December, union members overwhelmingly rejected a package that would have extended a now five-year freeze on cost-of-living adjustments to wages for an additional three years.

The new proposal offered a shorter, 16-month freeze in exchange for a total bump of 3 percent over the second 16 months of the contract

It also included additional money toward employee health care costs.

Pension cuts and additional cost-sharing by employees in retirement benefits were a part of both packages.

The union's previous contract expired in August. The new deal would extend to October 2015. If approved, it would go to the Board of Supervisors in March.

The standoff has been closely watched because any deal with SEIU could determine the outcome of contract talks under way with most other county employee bargaining groups. Agreement with a majority of the unionized employees is needed before proposed pay and pension cuts for managers, elected officials and other unrepresented workers take effect.

County officials say cuts are needed to free up money for government services and public infrastructure, including road repairs, and to pay off long-term liabilities to the county pension system, currently at $353 million.

Union officials have criticized the proposed concessions, which come amid a slow rebound in government revenue and after years of job cuts, pay freezes, unpaid furloughs and other reductions aimed to fill large, recession-era deficits.