Fairfax County officials, taking stock of the rising cost and declining ridership of Metrobus in the county, yesterday vowed to fight future increases in the county's contribution to the transit system.

Some members of the county Board of Supervisors also pledged to replace parts of the Metrobus system with independent, county-financed bus lines.

A week ago, the county awarded its first contract, for $2.1 million, to a private transit firm to take over the bus network in southeastern Fairfax County that feeds the Huntington Metro station. That line now is served by Metro. The service, scheduled to begin in September, is regarded by some Fairfax officials as a test of the viability of privately run bus systems in the county.

"We ought to draw the line in the sand and say we will pay our fair share and not one cent of tribute," said County Board Chairman John F. Herrity. "It's time for some healthy competition for Metro."

The board voted 6 to 0 to have its staff draw up a statement of its position on Metro funding. Supervisors Thomas M. Davis III, T. Farrell Egge and James M. Scott were not present for the vote.

In other action, the board gave final approval to a massive project in southeastern Fairfax known as Kingstowne, one of the largest developments proposed in the county in a decade, and endorsed a plan calling for relatively heavy residential and office construction around the Huntington Metrorail station.

On the issue of local funding for the Metrobus system, board members blamed high wages for Metro workers, who are represented by Local 689 of the Amalgamated Transit Union, and blasted the system of binding arbitration under which some Metro contracts have been settled in the past.

Herrity called Metro a "welfare program" for its workers, adding: "Now it's time to become more of a transportation system."

The county paid about $30 million in the current fiscal year to Metro, including about $6 million for Metrorail and $24 million for the more labor-intensive Metrobus. The total Metro operating budget is more than $400 million.

County officials expressed concern about a study of Metro funding recently launched by the Federal City Council, a prominent regional group made up of business and civic leaders. County Executive J. Hamilton Lambert said he expects the study to conclude that local jurisdictions "can afford the cost [of Metro] regardless" of the expense.

"The problem I have with that," Lambert said, "is that it does not address the question of how Metro fits in with the local priorities in each jurisdiction."

The Metro system is faced with dwindling federal funding and endangered state funding, and some area officials think it is inevitable that the localities will be asked to make up the difference.

Kenneth R. Sparks, executive vice president of the Federal City Council, called Lambert's comments "terribly premature" and said the group's final report is not due until October or November.

The Kingstowne project, located just south of Franconia on 1,170 acres of vacant land, was approved without opposition. The project, which will be worth an estimated $600 million, would include homes for 15,000 people and about 10,000 jobs, developers say. Fairfax officials say it would serve as a focal point for people in Lee District in the southeastern part of the county.

"This project is probably one of the last 'new towns' since Reston in Fairfax County," said Lee District Supervisor Joseph Alexander.