A former congressman and vocal critic of the Southwest light-rail project is raising concerns that a new federal spending measure could make it harder for the government to come up with its half of the $1.6 billion for the transit line.

The massive 2015 spending package Congress passed earlier in December gives priority to transit projects requiring less than a 40 percent federal share. The bill has no direct impact on Southwest, but could affect the project if similar criteria are applied to 2016 spending, when the much-debated line will need funding.

Former U.S. Rep. Martin Sabo said he believes language said the project has been pitched with the idea half the funding would be federal.

With the new guidelines for 2015, "I don't think that speech can be given … with a straight face anymore," said Sabo, who represented the Minneapolis area in Congress for nearly three decades. His daughter lives beside the line and is one of its most vocal opponents.

The line — which could open in 2019 — would run 15.8 miles from downtown Minneapolis to Eden Prairie. Its route through the Chain of Lakes in Minneapolis has provoked a federal lawsuit over environmental concerns.

Laura Baenen, a spokeswoman for the Southwest project, said it's too early to draw any conclusions about future funding changes. "To say what might happen after this [budget] is beyond anyone's knowledge," Baenen said. "It's just speculating."

At issue is a federal program known as "New Starts," which allocates general tax dollars to build new transit lines.

The 2015 appropriation gives the program $2.1 billion, but specifies that projects needing less than 40 percent federal funding — or which have secured a prior funding agreement — should get priority. Elsewhere in the bill is language prohibiting the funding of projects with more than 60 percent federal share.

The language represents a change from some previous measures, which merely capped the federal share at 60 percent, said Sarah Kline, policy director at Transportation for America.

"So that is a much bigger burden on the locals," she said, adding that most New Starts projects are seeking a 50 percent federal share.

It remains unclear how the new Republican majority in the U.S. Senate will affect those funds moving forward, though they are expected to face a close examination.

"People should not take the relatively calm history of the New Starts program as an indication that it's necessarily going to be that way forever," Kline said. "There's going to be a lot of discussion next year about domestic spending. And this is one of those programs that's going to be in the mix."

In addition to the 50 percent federal share, 30 percent of the project's $1.65 billion budget is expected to come from the seven-county transit sales tax. The remaining 20 percent would be split by the state and Hennepin County rail authority.

The project has submitted information to the Federal Transit Authority to be evaluated for possible recommendation in the president's 2016 budget proposal, the authority said Monday. That may be released in late winter. About half a dozen new projects around the country were recommended for 2015 funding.

Sabo said he believes the latest language, as well as some other recent Republican attempts to restrict New Starts funding, could prove to be major obstacles. "It's a clear indication of the direction the Congress is going in," Sabo said.

Eric Roper • 612-673-1732

Twitter: @StribRoper