The Loudoun County Board of Supervisors may now have enough votes to approve the extension of Metro's Silver Line into the county.

Loudoun supervisors must decide by July 4 whether to back the second phase of the rail project or to pull out, a move that would delay the project by up to two years and run up the costs for remaining partners.

Three of Loudoun's nine supervisors already support the rail project, and two others now say they may back it, giving the board the majority needed to approve spending of millions of dollars on it.

Hopes of extending the rail project into Loudoun were kept alive last week when the board overseeing the project, the Metropolitan Washington Airports Authority, dropped a controversial union-friendly labor agreement that Loudoun officials said would drive up the project's costs. But Loudoun officials said they've also made headway in devising a way to fund the project with minimal impact on taxpayers.

"I am increasingly comfortable that this is going to be an affordable project," previously undecided Supervisor Matt Letourneau, R-Dulles, said. "So I'm leaning towards supporting it."

A second supervisor who earlier opposed the project, Ken Reid, R-Leesburg, also says he may now be willing to back it -- but only if the county provides more money for roads or creates a special tax district so that only those who live near the Silver Line are paying for it.

"It's a major risk, but if I can get more money out of it for my district, I might be willing to support it," Reid said.

Three other supervisors are still undecided, and a fourth remains a vocal critic of the $6 billion project. Those lawmakers worry the project would be a financial burden on taxpayers.

"In general, I would like to see the project pay for itself and those that are going to benefit from it pay for it," said Supervisor Geary Higgins, R-Catoctin, who remains undecided.

Loudoun officials are still discussing options to fund the project, including the use of bonds, special tax districts or real estate tax increases.

The overall cost of the rail project would drop if Loudoun pulled out -- by as much as $530 million - but the Silver Line would look much different.

State, local and federal officials funding it would have to draft new financing agreements. The rail line itself would stop at Washington Dulles International Airport, requiring Fairfax County officials to provide the additional parking and infrastructure required by end-of-the-line Metro stations. Loudoun County, meanwhile, would lose millions in economic development and leave commuting residents without direct access to Metro.

"If we opt out of Metro, we would have a backlash from our citizens," Letourneau said. "They're strongly in favor of it. They've been told it's coming for years and years and years."