It was only a few months ago that city politicians gathered in Anacostia to break ground for the Green Line, a stretch of Metro subway that would finally enable lower- and moderate-income folk reasonable access to jobs and shopping enjoyed by the more affluent people who live along the Red, Blue and Orange Lines.

The speeches were so upbeat that the assembled crowd frequently broke into applause. After years of delays, there were smiles and backslapping as the shovels were turned.

Wilhelmina Rolark (D-Ward 8), told the crowd that they no longer had to look back at all the bad things that had happened. "We don't live in the past, do we? We live in the present," she said.

Now, it seems, Rolark and others should have at least been thinking about the future because last week the Office of Management and Budget recommended halting all federal spending for Metro subway construction, raising prospects that the long-delayed Green Line may never be completed.

The federal budget office proposed that federal appropriations for Metro construction be "zeroed out" in the next fiscal year, beginning October 1986, as part of a wide-ranging effort to reduce the federal deficit to a level set as a target for fiscal l987 under the Gramm-Rudman-Hollings bill.

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 cruel irony of this possibility is that it comes on the heels of another report by the Washington Council of Governments that concluded that low-income District residents face severe obstacles in commuting to blue-collar jobs in the suburbs because of inadequate public transportation.

Mainly because residents of Northeast and Southeast must use buses, trips to suburban areas where jobs are available usually take more than an hour each way.

The findings underscored widespread concern among District officials about the difficulties of matching unemployed D.C. residents with suburban jobs. The report said transportation poses a key problem for D.C. residents because most increases in jobs in recent years have occurred near the Capital Beltway and along highways outside the Beltway.

Metro officials concede that part of the problem results from delays in constructing the Green Line, the system's only unopened route.

Combine all of this with yet another recent report, this one by the Greater Washington Research Center, on the intransigence of poverty in the nation's capital, and it becomes clear that this subway line is not something that should be jeopardized.

One-third of the city's children are born into poverty from which there is virtually no escape, because generally their mothers are single with less than a high school education and no job and because the unemployment rate for young black men grew dramatically during the 1970s, the center study said. The percentage of unemployed black adult males jumped from 27 percent to 41 percent during the 1970s so that, by 1980, one out of every four black males in their late 20s and one out of every five in their 30s were not working.

With these factors deeply woven into the social fabric of this city, it seems incumbent on federal and local officials to do all that they can to make sure that at least a short segment of the Green Line -- say from Anacostia to Northwest Washington -- might be completed with existing funds, as soon as possible.

To do anything else would be just another cruel trick on the people of Anacostia. But the joke ultimately will be on the entire city for years to come.