The Federal Aviation Administration is pushing to revive a plan to build a heliport at Union Station and inaugurate helicopter service between Capitol Hill and surrounding metropolitan airports.

The proposal to install four or five helicopter landing pads atop the colossal train station's parking garage, and to run service costing $30 to $40 from the station to Dulles and Baltimore-Washington International airports, also has some backing from members of Congress and area business executives.

But neither the U.S. Department of Transportation, which is overseeing the renovation of Union Station, nor the D.C. government, which is completing the parking facility, is willing to take the lead on the heliport proposal.

"We think it's very likely a decision that falls on the District government to make sometime down the line," said Tom Blank, a spokesman for the federal DOT.

Thomas Downs, the District's director of transportation and public works, disagrees. "Unless the federal Department of Transportation and Congress are amenable to it, I'm not going to presume to make the decision for them."

Interest in the heliport was renewed this week, after Transportation Secretary Elizabeth Dole announced an agreement with Amtrak to spend $70 million to complete the restoration of dilapidated Union Station within five years.

The proposed heliport was mentioned in a Union Station planning study prepared for Dole's department by the consulting firm of Gladstone Associates. Two months ago, the D.C. Department of Transportation completed a study that concluded it would be structurally feasible to install a heliport on the roof of the parking garage for about $300,000.

However, city officials warned that a helicopter service from the train station might not be financially self-supporting. They also warned that the helicopter flights might encroach on the exclusive air space around the Capitol and White House and that noise from large transport helicopters might disturb residents.

"The FAA is very much interested in having it and there's a lot of private-sector interest in having it," said Gary Burch, the city's Union Station project manager. "But the District isn't in the position to make the final decision. That's somebody else's decision."

The FAA, which is part of the Department of Transportation, has pushed the heliport idea for several years, according to an FAA official who declined to be named.

Only a few cities, including New York and Houston, currently offer helicopter service from their downtown districts. The FAA hoped to encourage other cities to do the same by setting up a prototype in Washington, according to the official.

"It would make a more viable possibility for [quick] transportation between the downtown area and both [international] airports," the official said. "It becomes especially critical in trying to convince other cities to accept heliports . . . "

The Department of Transportation's reluctance to pursue the heliport project stems in part from the strong opposition to the proposal from another of its agencies, the Federal Railroad Administration (FRA).

FRA officials have complained that the heliport would use up 45 to 50 parking spaces in the garage that otherwise would generate revenue to help cover the train station's operating costs.

Downs, the District official, said the city intends to wait until the federal agencies settled their dispute over the proposal before getting any more involved.

"As long as there's the possibility for internecine warfare at the federal level, we want them to work that out," he said.