A new highway connecting Montgomery and Prince George's counties outside the Capital Beltway may cost $400 million more than previously projected, state highway officials said yesterday.

The price tag for an intercounty connector -- an 18-mile highway between Interstates 270 and 95 -- was estimated at $1.7 billion last year based on a 1997 study. But Maryland State Highway Administrator Neil J. Pedersen said yesterday that the projection has been revised upward, to a range of $1.8 billion to $2.1 billion, based partly on increased costs to reduce the road's environmental damage and improve nearby streams and wetlands.

By the time the highway is built, Pedersen said, the true price range will be closer to $2.1 billion to $2.4 billion, taking into account the cost of inflation in land prices and construction. Officials said they have not estimated financing costs of the project, which could take four years to build.

The highway would be paid for through state funds, money earmarked by Congress and bonds to be repaid with toll revenue and future federal highway funds, state officials said.

Pedersen said federal highway officials approved the state's construction budget last week, telling him they believed the estimates were "very conservative" and that there was "at least a 90 percent probability" that the final price would be lower. State House and Senate Appropriations committees are scheduled to hear an update on the highway's costs next week.

Gov. Robert L. Ehrlich Jr. (R) has called building an intercounty connector his top transportation priority, saying it would speed travel times between the fast-growing I-270 and I-95 corridors while reducing congestion on narrow east-west roads outside the Beltway. Critics charge that it would do too much damage to the area's streams, wetlands, wildlife and nearby neighborhoods.

One opponent of the highway who attended yesterday's news briefing scoffed at Maryland Transportation Secretary Robert L. Flanagan's assertions that the state would not only build an environmentally friendly highway but also clean up streams in its path.

"This is an attempt by the Ehrlich administration to try to greenwash the ICC, and it doesn't work," said Dolores Milmoe of the Audubon Naturalist Society.

"No matter how much money they throw at it, they're still putting down 18 miles of concrete."

State highway engineers are scheduled to release their draft environmental impact study of the highway later this month. Public hearings on the study are scheduled for January. The state will then seek the federal government's approval for one of two routes.

Pedersen said the state hopes to break ground on the road in fall 2006 and that drivers could use it as early as 2010. It would be a six-lane toll road with interchanges. The price of tolls would rise during peak times to keep traffic flowing freely.

Richard Parsons, president of the Montgomery County Chamber of Commerce, said the highway needs to be built before the price goes up with inflation.

"It's laughable that the opponents of this road are still denying the traffic benefits," Parsons said.

"It's about time they got out of the way. There's a clear political consensus to move forward on this project."

Montgomery County residents look over the proposed plan for the intercounty connector during a meeting held in June in Gaithersburg.