Metro officials, citing shortages of funds and other problems, have delayed their plans for opening the subway system's long-stalled Green Line and other rail extensions in the District, Maryland and Virginia.

Under the transit agency's newly revised schedule, the Green Line, Metro's only unopened subway route, will start service to Anacostia at the end of 1991, almost a year later than planned. Subway extensions to Montgomery County's Wheaton station and Alexandria's Van Dorn Street stop also will be delayed.

The rail system, once expected to be completed by the late 1970s or early 1980s, remains more than 30 miles and $2 billion short of its goal. With this month's opening of an Orange Line extension to Vienna, the system encompasses 69.6 miles. Metro's long-term plans call for a 103-mile rail network.

Prospects for expanding the system have been thrown in doubt because of recent moves by the Reagan administration to halt federal spending for Metro construction after this year. Key members of Congress have said they will seek to overturn the administration's plan and provide more funds for Metro.

The Green Line, which is designed to serve low-income neighborhoods where many residents depend heavily on public transportation, has repeatedly been delayed because of court battles, neighborhood controversies and shortages of funds.

Forrest T. Gay III, Metro's assistant general manager for design and construction, said that the latest delay in opening the Green Line stems from a refusal by the administration to release nearly $400 million in funds appropriated by Congress for Metro construction in the past two years.

Intensive negotiations are under way between Metro and federal officials over the issue.

According to federal and local officials, the negotiators appear to be close to agreement on a plan that may permit the administration to release the funds and allow Metro to complete at least 84.7 miles.

Gay said this dispute has hampered Green Line construction because the funds withheld by the administration include about $25 million needed for work on the planned Navy Yard station. The Navy Yard project, which must be completed before the Green Line opens, has been delayed 10 months, he said.

"I can attribute this to funding," Gay said. "We have no funds to base the contract award on."

Bonnie B. Whyte, spokesman for the federal Urban Mass Transportation Administration, said the agency could not respond to Gay's statement until it has reviewed the issue. Federal officials repeatedly have urged Metro to accelerate work on the Green Line, she said, adding that the transit system previously has failed to spend all of its federal funds.

In addition, Gay said, the opening of two Green Line stations in Northwest Washington -- those at Shaw and U Street -- has been postponed until late 1990, about four months later than planned. The setback resulted from disputes over Metro's rules governing participation in the projects by minority-owned companies.

Because of the delays on the Anacostia branch of the Green Line, officials said, the Shaw and U Street stations initially will be served by the Yellow Line, which connects the District's Gallery Place station with Fairfax County's Huntington stop.

When the Anacostia station opens in 1991, the Green Line will begin service between Southeast Washington and U Street, officials said. Service on the Yellow Line will then be modified to terminate at the Mount Vernon Square-UDC station, one stop north of Gallery Place.

A section of the Green Line linking Fort Totten in Northeast Washington with Prince George's Plaza is scheduled to open in late 1992. Gay said an extension to Prince George's County's Greenbelt terminus has been delayed by two years until 1994 and will be completed only if Congress allots more funds.

A Red Line extension connecting Silver Spring with Wheaton, which recently was pushed back from its 1989 target, has again been postponed and is scheduled to open at the end of 1990, Gay said. He attributed the latest delay to the holdup in federal funds and a newly required hearing over construction plans.

The opening of the Van Dorn Street station in Alexandria's West End will be delayed about three months until early 1991, Gay said. The postponement was caused by negotiations over relocating utility lines, he said.

No federal or local funds have been earmarked for other sections of the planned Metro system. Gay said he has not sought to assess when these extensions may open. Among the unfunded routes are two Green Line sections in the District and southern Prince George's, a Red Line terminus at Glenmont and a Franconia-Springfield terminus for the Yellow Line.