Metro officials, trying to get work moving on the system's troubled Green Line, named a new contractor yesterday to complete work on the Shaw-Howard University and U Street-Cardozo stations, still hoping to open the first section of the line next spring.

The action, under an unusual agreement designed to keep added costs to a minimum, follows the May 11 firing of Mergentime/Perini Joint Venture, whose work was a year behind schedule.

The new contractor, Perini Corp., has agreed to complete the two stations -- both of which are more than 80 percent finished -- for what it costs the company to do the work, no profit and no fees, said Metro spokeswoman Beverly R. Silverberg.

Perini Corp. was initially part of the joint venture but sold its interest in the project to Mergentime Corp. in 1987, according to the transit authority.

Although not involved in management of the project since then, Perini could be held liable as part of the joint venture if Metro wins a lawsuit to get the previous contractor to pay for completion of the project, Silverberg said.

"Clearly, it's in Perini's best interests to hold down the costs," she said. "Perini wants to get this finished, get it done well and get out."

The Green Line, Metro's only unopened line, is scheduled to open in three segments and will serve some of the region's poorest areas, where residents are most dependent on public transit.

The first section, which includes the Shaw and U Street stations, will run through the Seventh Street and 14th Street corridors, which have been torn up for years due to Metro construction.

"We are deeply concerned about the effects the Green Line opening delays have had on the residents and businesses in these neighborhoods and feel confident this action will bring these projects to a successful conclusion," said Metro General Manager Carmen E. Turner in a statement.

Metro officials said work could resume in late June under the agreement with Perini. They hope to have trains operating next spring from the existing Gallery Place-Chinatown station to the Shaw stop and on to the U Street-Cardozo station at 13th and U streets NW. A third stop along the first segment, at Mount Vernon Square-UDC, has been completed, under a previous contract with Perini.

The main work remaining at the two stations is installing escalators and elevators and repairing the streets.

In firing Mergentime/Perini, Metro officials said the contractor was in default on the two contracts because it allowed construction to fall behind schedule, failed to pay its suppliers and did not control the quality of its work and maintain safe conditions.

Mergentime/Perini has denied it defaulted on the contract and contends that the stations are behind schedule because Metro owes the company money. The initial contracts for the stations, after modifications, totaled $45.3 million and $57.4 million, and the bulk of those amounts have been paid.

Mergentime/Perini sued Metro a year ago for $18.5 million it claimed the company was owed. Those claims are still in litigation.