The Federal City Council, a private study group, has been chosen by the U.S. Department of Transportation to analyze mass transit needs in the Washington area through the year 2000 and the costs of providing bus and rail systems.

The $254,752 study, announced yesterday by Transportation Secretary Elizabeth Hanford Dole, marks the first time an agency independent of Metro has undertaken such an analysis.

Previous studies, conducted by the transit authority, have been sources of sometimes bitter disagreement among the local area governments that pay for the system.

"A common understanding of Metro's costs is essential to decisions about its future," said federal Mass Transportation Adminstrator Ralph L. Stanley. "The cooperation and assistance from the Washington area jurisdictions will be crucial for a realistic appraisal of local transportation plans and how future need will be financed."

The increasing cost of the Metro rail and bus system has prompted some rapidly growing suburban jurisdictions to create their own bus systems, and others are considering them. In addition, local lawmakers have encountered growing resistance from state legislatures to finance Metro in Washington.

The federal government under the Reagan administration also has pushed to hold down costs of local mass transit.

In a statement released yesterday, Dole said the study by the Federal City Council, comprising area business and civic leaders, will "serve as a model for other areas that are examining the financial implications of building and operating complex transit systems."

"There is great concern around the area about the potentially rising costs of the Metro system," said DOT spokeswoman Bonnie Whyte. "It really needs a very long hard look by a central body that can provide an impartial view to the whole thing."

Some local leaders, among them Arlington County Board Chairman John G. Milliken, until recently the chairman of Metro, have been meeting for several months with the Federal City Council to map out the study.

The DOT is expected to ask each jurisdiction to appoint a representative to a study task force.

David Perry, deputy director of the council, said the study will focus particularly on demands for bus service, which have become a growing concern for local legislators as the population around the Beltway continues to grow outward.

"We have a pretty good handle on what the rail system will be," Perry said. "The bus system is a lot more difficult to assess because nobody can tell you with precision, for instance, what the bus network will be in rapidly growing Fairfax County or who will be operating it."

Officials said they hope the study will be completed before the end of this year.