Maryland transportation officials announced yesterday that a two-mile stretch of the Capital Beltway in Prince George's County will be widened from eight lanes to 10 beginning next year, a plan designed to relieve pressure on one of the most troublesome traffic spots in the state.

Construction on the $15.7 million project is expected to begin in July and take about 14 months to complete. State officials said existing lanes will not be closed during rush hours, but that some inconvenience to motorists will be inevitable during construction.

News of the project comes at a time when officials in both Maryland and Virginia are desperately searching for ways to avoid gridlock and accommodate the ever-increasing number of vehicles using the Beltway to travel in and around Washington and its expanding suburbs.

Proposals for building eastern and western bypasses to the Beltway have been under serious consideration in both states for about a year. Last week, Virginia transporation planners unveiled a $1 billion proposal to widen the state's entire 21-mile section of the Beltway from eight to 14 lanes. No funding is available for that proposal.

The plan announced yesterday will add a fifth lane to the outside of both the inner and outer loops of the Beltway between Route 1 and New Hampshire Avenue (Route 650). The project will also increase the road's capacity where I-95 branches off the Beltway.

Officials said no additional right of way will be needed for the new lanes, which will be formed from the road's existing wide shoulders.

Gov. William Donald Schaefer revealed details of the project yesterday while campaigning for Democratic legislators in Prince George's County. The governor's spokesman, Paul Schurick, said the surprise announcement followed the federal government's decision on Friday to finance 90 percent of the project's costs. The state will contribute the remaining $1.6 million.

"There is no question that this area of the Beltway is one of the worst bottlenecks on the Beltway and possibly the worst bottleneck on the Maryland side," Schurick said.

State Del. Timothy F. Maloney (D-Prince George's), who chairs a House subcommittee that handles transportation funding, said that by comparison to the Virginia project, the plans for Prince George's are modest. But he said the improvements will provide a much-needed solution to a problem area that plagues thousands of commuters each day.

According to Maloney, the project consists of three sections, two on the outer loop and one on the inner loop, although work will proceed on all of the segments simultaneously.

On the outer loop, a lane will be added to carry traffic from the Route 1 exits in College Park to where the Beltway and I-95 north currently split off into two lanes each. In addition, one of the two ramps leading from I-95 south onto the westbound Beltway will continue to New Hampshire Avenue. Currently, both lanes end.

On the inner loop, a fifth lane will be added from New Hampshire Avenue North to the Route 1 exits, where the northbound exit will be upgraded to include an improved area for vehicles to merge, Maloney said.

Maloney said yesterday that the portion of the Beltway slated for expansion has become a problem area in recent years because of booming commercial and residential development in Howard, Montgomery and Prince George's counties.

The outer loop, which is a major route for commuters traveling to large employers along I-95 and I-270, is usually congested in the mornings, while the inner loop is clogged during the evening hours, he said.

Schurick said that Maryland State Highway Administrator Hal Kassoff began seeking federal funding for the project about two years ago and negotiations with federal transportation authorities intensified earlier this summer.

Russell Ulrich, a spokesman for the State Highway Administration, said that despite the small scope of the project, "any widening of the Beltway is going to help."

Asked about traffic problems during construction, Ulrich said, "There might be some lane closures during the day, but certainly not during the peak hours . . . . Any time you have construction along the roads there are going to be problems, but we do everything we can to keep that to a minimum."