U.S. Transportation Secretary Ray LaHood will try to make peace Wednesday between the key players shaping the future of the Metrorail extension to Dulles International Airport. Debate between the board overseeing the project and the local and state officials helping to pay for it has centered on the cost and location of the airport station.

But the issue has touched off broader concerns about the overall price tag, viability and management of one of the nation’s largest mass transit projects.

With the stalemate over the airport station threatening to derail the project, LaHood offered to intervene and said last week that he hopes to come out of the meeting in his Southeast offices with “an agreement on a way forward.”

The federal government has pumped nearly $1 billion into the project, and the transportation secretary said it “will go forward; it will be completed. It’s too important to the people of this region.”

It is unclear, however, whether LaHood can mend rifts in what is a fragile coalition of regional partners with competing interests.

Construction is underway on the first phase of the 23-mile rail line, which will have four stations in Tysons Corner and end in Reston. At issue is the second leg to the airport and into Loudoun County.

The Metropolitan Washington Airports Authority, which is managing the rail project, voted in April in favor of building a tunnel and underground station with an eye toward convenience for airline passengers and preservation of the views of the terminal designed by architect Eero Saarinen. The authority, led by a board appointed by the Virginia, Maryland, District and federal governments, also operates Reagan National and Dulles airports and the Dulles toll road.

The board’s decision outraged the elected leaders of Fairfax and Loudoun counties and officials at the state level, who had urged the airports authority to choose a less expensive aboveground station. In the weeks since the vote, local, state and federal officials have pressed the airports authority to reverse course and to scale back the cost of the second phase of the project.

“We are at an impasse,” said Rep. Gerald E. Connolly (D-Va.), who called it “untenable” for the airports authority to proceed on its current path. “We’ve got to find a way to make sure it works and that we don’t wittingly or unwittingly jeopardize this project.”

LaHood would not say in an interview whether he has a preference for the airport station location, but he made clear that he, too, is concerned about cost.

“We don’t have a bottomless pit of money,” he said.

The Fairfax and Loudoun governments, which are slated to contribute 16.1 percent and 4.8 percent of the cost, earlier agreed in concept to a plan that included an underground station and had a preliminary cost of $2.5 billion. But with the cost now at $3.5 billion, Loudoun is exploring the possibility of pulling out.

Connolly and Rep. Frank R. Wolf (R-Va.), who represent Northern Virginia, have also expressed frustration with the rising cost. And Wolf introduced legislation last month that would make it easier to remove members of the airports authority board.

The immediate question is whether the airport station should be built aboveground in front of the airport’s daily parking garage or underground and closer to the terminal. It is a difference of about $330 million. For airline passengers, it would mean traveling an additional 600 feet on an indoor moving walkway.

Robert Clarke Brown, the airports authority finance committee chairman, and other proponents of the underground option said the board shares an interest in shaving the overall cost of the project and is looking at options such as privatizing the construction of parking garages.

Former Maryland governor Parris N. Glendening (D), president of Smart Growth America’s Leadership Institute, urged the board to stick with the underground station. He recalled the fight over where to locate the College Park Metro station during his tenure as Prince George’s County executive. The station, he said, should have been located in the heart of the University of Maryland’s campus to encourage more students to take Metro to classes and basketball games.

“You don’t buy the cheapest car, the cheapest suit or the cheapest food product. We buy something healthy that’s going to last,” Glendening said. “Yes, we may have to pay a little more now, but if we really do it correctly, it’s an investment that’s going to pay off.”

But in choosing the underground option, the board rejected the advice of airports authority President and Chief Executive Officer E. Lynn Hampton and the Metropolitan Washington Airlines Committee, which represents the airlines serving National and Dulles airports.

Chief among the concerns of local officials is the cost to taxpayers and toll road users. A major chunk of the project — more than 50 percent — would be paid for with revenue from future toll increases.

The airports authority financial analysis shows, however, that the location of the airport station will have a minimal effect on how much commuters on the toll road pay. What is critical to the financing plan — and the price of tolls — is the award of a low-interest loan from the federal government through the Transportation Department.

The $2 one-way fare would have to to double to $4 in 2015 with the loan. Without it, according to the analysis, tolls would have to rise to at least $5 and increase to more than $10 in 2020.

Virginia Transportation Secretary Sean T. Connaughton called the board’s expectation of a $1.7 billion loan “simply not realistic.”

“No one in the history of the program has received that much money, and there isn’t that much money available. You’re building a house on sand,” he said.

The Metrorail project is one of 40 nationwide that have expressed interest this year in the federal financing pool of $1.1 billion. In past years, the program awarded a $516 million loan for the Intercounty Connector and $589 million for the Beltway HOT lanes.

Despite their differences, the stakeholders have a shared interest in finding common ground when they meet Wednesday with LaHood. A successful loan application depends on cooperation among the local partners — and LaHood, who signs off on the loans.

Brown, the finance committee chairman, acknowledged the competitiveness of the loan process but noted that the board’s financial consultant helped set up the DOT program and is well-versed in navigating the system.

“Our advisers would never have submitted a request that size if we didn’t believe it was feasible,” he said, adding that the board would stick with its decision “until we conclude it’s not financially feasible.”