A rendering that depicts a Purple Line tunnel that would run beneath Bethesda. (Courtesy of Maryland Transit Administration)

Prince George’s County business and political leaders on Thursday called for state money to build a Purple Line through the Maryland suburbs, citing a light-rail line’s ability to attract jobs and rejuvenate communities around stations.

The Purple Rail Alliance, a group of business and civic leaders, made its public debut at a briefing about the rail proposal’s potential to spur economic development.

“This is exactly the kind of coalition that got the Silver Line out to Dulles,” Prince George’s County Council member Eric Olson (D-College Park) told a crowd of about 100 at the Greenbelt offices of the Bozzuto Group development firm. “This is exactly what we need.”

State transit planners said Purple Line plans are at a critical point because construction cannot begin on schedule in 2015 unless the state finds new money within the next year to cover half of an estimated $1.93 billion in construction costs. The state plans to seek highly competitive federal funding for the other half. The proposed 16-mile line between Bethesda and New Carrollton is scheduled to open in late 2020 but has no construction money.

Henry Kay, the Maryland Transit Administration’s head of transit development, told the group that Purple Line construction costs have risen to $2.2 billion. But Kay later said that the amount given was “for legislative planning purposes” and that the state is still updating the cost projections.

“We’re at the point where without significant additional revenue, we’re going to need to slow the process down,” Kay said after the briefing.

A proposal that Maryland Gov. Martin O’Malley (D) pushed during this year’s legislative session to raise the gas tax died amid rising gas prices and an outpouring of anti-tax sentiment. Any transportation tax increase that fails next year probably wouldn’t be proposed again until 2015 because lawmakers would be especially reluctant to raise taxes in 2014, when the entire General Assembly is up for election. But state officials said they need to secure state funding by 2014 to stay on schedule.

“It’s either going to be a difficult journey ahead or an exceedingly difficult journey ahead,” Maryland Lt. Gov. Anthony G. Brown (D) told the group. “But we’re going to make it happen.”

Alliance leaders said a Purple Line would create 7,000 construction jobs and 400 jobs to operate the line.

University of Maryland President Wallace D. Loh told the group that the College Park campus needs light-rail service to continue attracting top faculty members and students.

“We can’t be landlocked by impossible traffic conditions,” Loh said.