The closer Washington area leaders seem to get to a compromise on extending Metrorail to Dulles International Airport, the more tenuous the negotiations appear.

Elected officials from Fairfax County, who are big investors in the rail line, expressed reservations Tuesday about taking on greater responsibility for the second phase of the project without a firm commitment for more money from the state government.

The concerns from members of the Board of Supervisors came one day after Virginia Gov. Bob McDonnell (R) said the state has not put “a dime of new money on the table, and at this point we don’t have any plans to.”

Those comments did not sit well with supervisors who are weighing a proposal brokered by U.S. Transportation Secretary Ray LaHood, to cut the cost of the $3.5 billion rail project that would extend Metro to Dulles and into Loudoun County.

Under LaHood’s plan, Fairfax would take responsibility for building the planned Route 28 Metro station and for construction of several parking garages. In exchange, LaHood has said his department would make federal loans available to the county.

“What shared sacrifice is being borne by the state?” asked Supervisor Jeff McKay (D-Lee). “The governor said zero money would come from the state. I don’t want to act on anything until I know if the state is going to pull up a chair and be a player.”

The Metropolitan Washington Airports Authority, which is managing the rail project, has also called on the state and the federal government to make a larger contribution to the project.

In a presentation to the Fairfax board Tuesday, Federal Transit Administrator Peter M. Rogoff had a more optimistic take on McDonnell’s message from the previous day. Rogoff said he had spoken with Virginia’s Transportation Secretary Sean Connaughton during his morning commute and that “we believe when all is said and done, you’ll see a commitment for $150 million from the commonwealth.”

“What you’re seeing here is reticence of the different parties to all jump in the cold pool immediately at the same time,” Rogoff told the board of supervisors.

He urged the board to make a decision before the next meeting with LaHood and other stakeholders July 20 that would “articulate with clarity whether they are in or out.”

Connaughton was not immediately available to comment.

Board of Supervisors Chairman Sharon Bulova (D) echoed Rogoff’s theme, saying all parties “need to be prepared to hold hands together, to jump together, knowing that everyone is prepared to do their part.”