Montgomery and Prince George's counties will need an infusion of private funds to build the Purple Line, as state and federal funds for transportation projects grow increasingly scarce, according to Montgomery County Executive Ike Leggett.

Montgomery County's backlog of transportation funding needed for both local and regional projects is rapidly approaching $4 billion, Leggett told the Maryland General Assembly at a joint House and Senate hearing Tuesday.

Local officials are doing all they can to identify funding for roads, buses and rail projects, but they need help, he said.

"We can't solve these problem overnight and we certainly can't solve them by 'going it alone,' " he said. "Developing and maintaining transportation infrastructure is a partnership, and Montgomery County is doing its part."

Maryland officials have operated under the assumption that federal money would pay for large sums of their transportation infrastructure needs, such as the Purple Line, the planned 16-mile light rail extending from New Carrollton to Bethesda.

Recent estimates place the price tag for the project, estimated to be finished in 2020, at $1.93 billion.

Officials have expected the federal government to pick up about half the bill for the new rail project, but now face the reality that those funds may not be available.

"In this economy, we have to be creative. Yes we're going to pressure the federal government [for funds], but it may not be there," Prince George's County Executive Rushern Baker said on WTOP.

The potential for redevelopment is greatest in Prince George's, but the Purple Line is a waste of money when there are other areas of the county already ripe for construction, according to Ajay Bhatt, president of the Friends of the Capital Crescent Trail, a group that opposes the light rail.

"Fourteen of the 15 Metro stations in Prince George's County don't have the kind of development that they're talking about, that would spur economic growth," Bhatt said. "So why are we talking about spending on new infrastructure when we don't have development around our current infrastructure?"

Tom Farasy, co-chairman of the Purple Line Alliance, said each county should be open to a variety of potential revenue streams to fund the project, which could have a "mammoth" economic effect.

Businesses in particular should consider the wealth the Purple Line is projected to attract before declining to chip in, he said.

"We're very supportive of not only that, but any and everything, because it's clear the federal government is not just going to write a check," Farasy said. "It's probably going to be even more demanding once Congress gets through its debt ceiling issues."

Rachel Baye contributed to this report.