Bowing to pressure from Prince George's County, the Metro Board yesterday recommended a four-year construction program that would complete land purchases and break ground on all remaining segments of the planned 101-mile system by 1985.

The $1.8 billion plan would also expand operating lines from the current 37 miles to 70 by early 1986 and resume construction on the long-delayed inner-city Green Line. It now goes to the local jurisdictions for approval. After that, applicants will be filed with the federal government for the first year's funding.

In closed-door talks with the other seven local governments in the Metro system over the past month, Prince George's had demanded that construction of lines to Greenbelt and Rosecroft be well under way by the mid-1980s and threatened to delay the agreement.

With only five of its 14 miles of track constructed, Prince George's County feels it was shortchanged. Now, amid fears that federal grants may dry up in the mid-1980s, county officials worry that their routes, scheduled to be among the last built, may never be built at all.

Federal funds cover most of Metro's construction costs. The Reagan administration has not ruled out financing a 101-mile sytem, but to date has committed itself only to 75 miles. Prince George's hopes that if a crunch comes, half-built stations and tunnels will attract more federal dollars than ones that haven't been started.

The plan calls for about $151 million to be spent in Prince George's in the first three years, compared with $63 million that Metro staff members had originally recommended. c

Much of the extra money was diverted from Montgomery County's Rel Line to Glenmont, delaying completion there by at least a year. Yesterday Ed Rovner, an aide to Montgomery County Executive Charles Gilchrist, condemned what he called Prince George's "holding the whole system hostage for its will." But Rovner said the county was basically satisfied with the solution.

Ray La Placa, a Prince George's board member, rejected Rovner's allegations. "No one was held hostage to anything," he said. "There was a great deal to give and take in negotiations." La Placa said the agreement was "probably the best I have a right to expect."

Under the plan, the District governemnt would get nearly $90 million per year to press ahead with the portion of the Green Line that will link Anacostia with the Shaw station in Northwest, a major priority of Mayor Marion Barry.

In extending operating track from the present 37 miles to 70 by 1986, the plan would open the Blue Line through to Hunington and begin Yellow Line shuttle service from Gallery Place across the 14th Street Bridge in late 1982. The Red Line would open to Shady Grove in late 1983 and the Orange Line would begin service to Vienna in early 1986.

But Metro officials caution that funding uncertainties make completion dates for the final 31 miles of the system highly speculative, although estimates ranging from the late 1980s to the early 1990s are commonly heard.

Those final segments are most of the Green Line from Rosecroft to Greenbelt, the Red Line from Silver Spring to Glenmont and the Yellow Line from King Street in Alexandria to the Franconia-Springfield terminal.

However, under the plan, Metro would have purchased all land, finished the costly process of designing stations and tunnels, and begun constructing on all lines 1985.

This schedule differs significantly from one drafted by Metro staff members and used as the original basis of discussion by the transit system's special Ad Hoc Committee on Construction. The committee includes representatives of the eight jurisdiction and meets in closed session to debate ways to divide up the funding pie.

One month ago, Prince George's member David Hartlove introduced the county's new proposals.

The committee works by consensus, which gives any member effective power to hold up agreement indefinitely. But compromises were worked out.

"Prince George's did a good job for themselves," committee Chairman Joseph Alexander said yesterday, although he and Metro General Manager Richard Page stressed that the plan offered something to all eight governments.

Extra funds for the county were obtained in part by lopping $23 million in construction funds from Montgomery County's Red Line.

In addition, real estate purchases for the Franconia-Springfield leg of the Yellow Line in Fairfax County were spread over two years.

The plan calls for purchases to be completed within four years.

The plan also laid donw new provisions regarding how much individual governments would pay into Metro's construction coffers. It would link a jurisdiction's payments proportionately to how much construction is going on there during a particular fiscal year, rather than to how much will eventually be completed. That means Prince George's will pay slightly less than in past years until construction speeds up.

It also stipulates that if federal funding is reduced, any resulting construction slowdown should be spread around the jurisdictions equally.

General Manager Page emphasized that the entire plan hinges on how much money the federal government actually provides. Funding is reasonably ceratin only for fiscal 1982, with appropriations bills now before Congress giving Metro $315 million. For fiscal 1983 the Office of Management and Budget has provided a "guidance number" of $275 million. Metro planners have simply guessed the government will provide $375 and $415 million for the two following years.