In high-level meetings, Maryland and Virginia have been quietly exploring the possibility of an agreement on the ambitious and still evolving outer beltway, a proposed 150-mile highway ringing Washington and its suburbs.

Last month, Maryland Highway Administrator Hal Kassoff and Virginia Transportation Commissioner Ray Pethtel met privately to discuss a joint study of the $1 billion highway project, officials said. An agreement between the states is by no means certain, they said.

"There is a difference of views," Kassoff said. "There is a question of whether we will even agree on a study." He added, however, that the two states plan to "keep on talking."

Based on an idea that dates to the 1950s, the proposed highway, which would include two new bridges across the Potomac River, is aimed at siphoning vehicles from the traffic-choked Capital Beltway, improving access to Washington's growing outer suburbs and providing a bypass for traffic passing through the Washington area.

In its latest incarnation, the outer beltway actually consists of two roads, one skirting the region to the west and the other to the east. The two states have never agreed over which section of the road should be built first.

Virginia favors a western leg beginning at I-95 near Quantico, crossing the Potomac River near White's Ferry, connecting with I-270 and I-70 in Maryland and rejoining I-95 north of Baltimore.

Maryland favors an eastern leg that would follow Rtes. 3 and 301 from Baltimore to southern Prince George's County, turn west through Charles County and cross the Potomac near Dumfries.

Each state is pursuing an independent study of its own leg. If the two states could agree on a joint study, it would mean they were willing to consider giving up their insistence on one leg over the other, a big step with so much at stake, according to a source close to the discussions.

In Northern Virginia, the powerful real estate industry has thrown its weight behind the western leg of the outer beltway, viewing it as a boon to development in western Loudoun County.

On June 23, the two commissioners met in Northern Virginia to see if they could agree to the study, officials said. Although the meeting did not produce an agreement, Kassoff said, "the fact that we are talking to them is positive."

Kassoff declined to comment on why the meeting failed to produce an agreement, saying that the negotiations have reached a sensitive stage. "I can't get into the specific issues without affecting the discussion process," he said.

Officials in both states said they are committed to the outer beltway in one form or another.

"Obviously, if we're going to build a western bypass, we need to connect up with something in Maryland," Pethtel said. "And they need to connect with something in Virginia." He said he plans to meet again with Kassoff in August.

Virginia Gov. Gerald L. Baliles and Maryland Gov. William Donald Schaefer have discussed the subject informally, according to a source close to Baliles, although not "in any substantive way," a spokeswoman said.

The spokeswoman said the discussions between the states are being handled by the secretaries and commissioners of transportation, although she added, "Depending on what happens there, the governors could get involved later."