Maryland and Virginia transportation officials, hoping to end a standstill over the best route for a new superhighway to relieve traffic congestion on the Capital Beltway, announced an agreement yesterday to study options for the so-called Washington Bypass through the region's outer suburbs.

Progress on the long-planned bypass has been stalled by a stalemate between the two states over what path the road should follow. Maryland officials want an eastern route, while their counterparts in Virginia have said the highway should skirt Washington to the west.

Yesterday's agreement, while not ending the conflict, is a major step off dead-center for the two highway bureaucracies, which will jointly fund and oversee an engineering study aimed at forging a "consensus on need and priority" on the two bypass options, Maryland Highway Administrator Hal Kassoff said.

"We'll both be singing from the same songbook" once the study by a private firm is completed in 1989 at a cost of more than $1 million, Virginia Transportation Commissioner Ray D. Pethtel added.

Most regional transportation officials have said they hope both legs of the Washington Bypass will be built eventually, but because it is unlikely that they could be started simultaneously -- and either state could effectively block the other's proposal -- resolving the east-versus-west issue is essential.

Said Kassoff: "We each have our goals, we each have our preferences. But in the long run, we have to work together."

Virginia Gov. Gerald L. Baliles and Maryland Gov. William Donald Schaefer have discussed the subject of a Washington Bypass informally, according to aides, most recently Wednesday night in Norfolk, where the two were attending a regional conference on cleaning up the Chesapeake Bay.

Different routes for the eastern and western legs of the bypass remain in contention. In general terms, however, the eastern highway would veer off I-95 near Dumfries in Prince William County, cross the Potomac River into Maryland, travel north along Rte. 301 through Charles and Prince George's counties, and continue on Rte. 3 into the Baltimore area.

The rough path for the western bypass would cut off I-95 near Quantico in Prince William County, steer toward western Loudoun County, cross the Potomac near White's Ferry, connect with I-270 and I-70 in Maryland and join I-95 again north of Baltimore.

Although Maryland and Virginia will split the cost of the engineering study, each state will retain a stake in its preferred route: Virginia overseeing the analysis of possible western routes, and Maryland overseeing the study in the east. Two reports will be released at the end of the study, with a single summary.

The agreement, announced at a morning news conference at the American Automobile Association's offices in Fairfax County, was reached after intense negotiations between Pethtel and Kassoff during the last few months, officials said.

A Washington Bypass has become crucial, many of the region's transportation planners contend, as the Capital Beltway has evolved from a way for interstate traffic to avoid the District of Columbia into a badly congested Main Street for local traffic in the suburbs. At least two-thirds of the trips on the Beltway begin and end in the Washington area, a recent study found.

If the bypass proposals continue to gain momentum, they promise to incite some of the most monumental political battles in recent history. Highway proposals can always expect opposition from neighborhoods in their path; but the proposed western bypass, particularly, is already stirring a storm of angry local protests.

The western path would cut through Loudoun near the hunt country estates of some of the area's wealthiest residents. These people and other opponents of growth there have railed against the western bypass and other road proposals. A popular item in the county is a bumper sticker that reads: "Don't Fairfax Loudoun!"

However, the western bypass also has some powerful friends, including Northern Virginia developers such as John T. (Til) Hazel, who owns large tracts near the proposed bypass.

How to foot the bill for the two bypasses -- estimated at $1 billion -- is also uncertain. The federal government paid for 90 percent of the 42,500-mile interstate system, but with that program being phased out of existence, it is unclear what role federal money will play in constructing support roads for the interstates, said Kassoff.

One option would be to finance the highways with tolls, as was done with the Dulles Toll Road.

Critics of the bypass proposals have charged that the roads would do less to steer traffic off the Beltway than to provide new opportunities for developers to open up unspoiled land in Washington's outer suburbs.

Sensitive to the accusations, Pethtel said the state governments will work closely with local communities to determine the extent of development a bypass might create. He said the impact of a western bypass on growth could be checked by limiting interchanges to major roads such as Rtes. 50 and 7.

Also announced at yesterday's news conference was the renaming of a group that was formed to promote support for the Washington Bypass. The Traffic Research Foundation, which came under fire for being too closely aligned with developers, has been rechristened the Develop Outer Interstate Thruways Coalition.

The group's new chairman, former representative Michael D. Barnes (D-Md.), said the new acronym -- DO IT -- will symbolize the group's boosterism for improvements to the Capital Beltway and progress on the Washington Bypass.