Six Republican lawmakers banded together Monday to criticize plans by Virginia Gov. Bob McDonnell's administration to build what opponents call an "outer Beltway" through rural Northern Virginia, saying the state's plan would create a "traffic nightmare" for drivers.

Politicians and about 20 local residents gathered Monday to announce their opposition to the project, which would involve closing portions of Route 234, which cuts through the Manassas National Battlefield Park -- a change the opponents said would push more cars to already congested Interstate 66.

"We think this is the next battle of Manassas," said Del. Tim Hugo, R-Centreville. "The National Park Service, the Commonwealth Transportation Board and the Virginia Department of Transportation are declaring war on I-66 commuters."

Hugo was joined by Republican state Sens. Jill Holtzman Vogel, Dick Black and Richard Stuart and Dels. Bob Marshall and Michael Webert.

Residents said the change would mean longer commutes to and from Washington, and that the state should focus on fixing commuter routes into the city, instead of north-south connections between rural areas.

"We rely on 66," said Gainesville resident Linda Budreika. "It's going to put a horrible traffic nightmare on Route 15 and Interstate 66. It's a bad decision."

But opponents also took issue with the larger plan for an outer Beltway -- or as state officials call it, the "North-South Corridor" -- with Vogel, R-Winchester, calling it "unbelievably costly" and "devastating." Opponents say the road would cost at least $1 billion, while supporters say the price tag can't be known until the state has a firm design for the highway.

State officials say actual construction on the corridor is a few years away, but opponents worry the state will sign the dotted line on the road by the end of this year.

"I think they are trying to force this quietly," Hugo said.

Virginia Secretary of Transportation Sean Connaughton said the road is needed to cope with booming population in Northern Virginia's exurbs, and that the state could start adding express lanes or buses to I-66 by the end of the year to deal with any extra traffic brought on by the closing of the routes through the battlefield.

"This project has been around for well over 20 years," Connaughton said. "It was needed 20 years ago. It's needed today, and it's going to be needed even more in the future as you continue to see both Prince William and Loudoun County grow."