The Office of Management and Budget has recommended halting all federal spending for Metro subway construction, raising prospects that the long-delayed Green Line and other proposed rail extensions may never be completed, according to congressional and other sources.

The proposal, now being reviewed by federal transportation officials, would represent one of the most dramatic setbacks for the Washington area to result from landmark balanced-budget legislation approved by Congress and signed by President Reagan this week.

The federal budget agency proposed that federal appropriations for Metro construction be "zeroed out" in the next fiscal year as part of a wide-ranging effort to reduce the federal deficit to $144 billion, the level set as a target for fiscal 1987 under the Gramm-Rudman-Hollings measure, the sources said.

Under the OMB proposal, the transit authority would likely have only enough federal money to expand the rail system to slightly more than 70 miles, far short of the 103-mile plan advocated by Metro and other local officials.

The proposal would not endanger the opening of a nine-mile Northern Virginia extension of the Orange Line to a Vienna terminus, scheduled for June 7, because construction work there is virtually finished, officials said.

But, officials said, it is unclear whether the proposal would allow the authority to complete any part of the Green Line, Metro's only unopened route. Delays in building the Green Line have stirred concern among local and federal officials because the route was designed to serve low-income neighborhoods where residents depend heavily on public transportation.

One transit analyst said it appeared possible that a short Green Line segment between Anacostia and Northwest Washington might be completed with existing funds. Portions of the Green Line stretching into Prince George's County probably could not be constructed, the analyst said.

A proposed Red Line extension from Silver Spring to Glenmont in Montgomery County and a Yellow Line branch from King Street in Alexandria to a Franconia-Springfield terminus also would be threatened under the OMB proposal, officials said.

A Metro spokesman declined to comment on the OMB plan, saying that any proposed cutbacks would have to be reviewed by the authority's board of directors. OMB officials also declined to comment.

Congressional sources said they had been told that Ralph L. Stanley, the Reagan administration's mass transit chief, plans to seek to overturn the OMB proposal. "This is not the end of the game," one source said. A spokesman for Stanley refused to comment.

The proposal, disclosed yesterday by The Wall Street Journal, drew immediate protests from spokesmen for Washington area members of Congress, including Sens. Charles McC. Mathias Jr. (R-Md.) and John W. Warner (R-Va.) and Reps. Steny H. Hoyer (D-Md.), Stan Parris (R-Va.) and Frank R. Wolf (R-Va.).

Administration proposals to cut spending for transportation have repeatedly been rebuffed by Congress. Sources said the new OMB plan would eliminate Amtrak subsidies and sharply reduce most mass transit aid. This week, Senate and House conferees balked at cutting Amtrak funds by authorizing $1.8 billion over three years.

The Metro system already is embroiled in a fiscal crisis because of federal cutbacks and cost overruns. This week, Senate and House conferees approved a compromise $227 million allocation for Metro for the current fiscal year, an amount considered adequate to carry out the agency's construction plans for that period.