New federal legislation will cause further delays in Metro's rail construction, but will give the transit system $6 million more than expected in federal operating aid, easing upward pressure on fares and subsidies from area governments.

The long-delayed "inner city" Green Line will be most affected by the construction cutbacks, Metro planners believe. The opening date for the line between Anacostia and Mount Vernon Square-UDC has now been pushed back six or nine months more, to late 1989 at the earliest.

The Transportation Appropriations Act, signed by President Reagan Saturday, provides about $20.2 million in operating aid for Metro, according to the U.S. Department of Transportation, or $6 million more than Metro officials had expected. Other legislation now before Congress would allow Metro to divert some capital grants to help pay operating costs if it chose.

Metro has proposed an April fare increase to help reduce deficits that are expected to reach $180 million this fiscal year. The extra federal operating aid could be used to hold down that increase, or to reduce local governments' payments to Metro.

The law also provides for $285 million in federal funds for Metrorail construction for fiscal 1983. Metro had counted on $90 million more than that, and is now revising its plans. Those plans are subject to federal approval.

Original plans called for Metro to commit $95 million for fiscal 1983 to Green Line construction, but that commitment has now been reduced to $44 million.

Due to a court order that blocks work on the southern part of the line, most of the money will be used to dig tunnels 2,000 feet north from Gallery Place.

George Earnhart, Metro's assistant director of program control, estimates the cut in funds will push opening of the Green Lines' first stage, a shuttle between Mount Vernon Square-UDC and Anacostia, from early 1989 to late that year -- assuming there are no further problems. Service should be extended to U Street NW a year or so later.

Opening dates for those and other largely unstarted segments in the full 101-mile rail system are highly speculative, due to rising costs, challenges in court and Reagan administration statements that it will fund only a 75-mile system for now. Some area transit officials fear some parts of the unstarted segments will never be built.

In Virginia, Metro had planned to spend $15 million buying land for the line to Franconia-Springfield and $5 million to build bridges over highways and railroad tracks along it, the first construction on that segment, which is now projected to open in 1991.

All 1983 funds for this section have now been canceled, though Metro still has about $5.5 million for real estate for it from earlier years. Virginia's 1983 funds will be concentrated on the Orange Line to Vienna, targeted for a 1986 opening. "We're confident that we can maintain schedule," Earnhart said.

The money will be used to lay track, install kiosks and power substation gear and buy communications and automatic train-control equipment.

Under the revised plan, Metro hopes to spend $7 million on real estate on the Green-Yellow route to Greenbelt and $600,000 for land along the Green Line to Rosecroft, a reduction from earlier plans.

It also provides $25 million toward building the West Hyattsville station and track bed to the District line.

The planned opening date is the early 1990s for Greenbelt and sometime in the 1990s for Rosecroft.

It remains unclear whether federal officials will approve Metro's revised 1983 proposals for Greenbelt and Rosecroft, because the lines there appear to lie beyond a 75-mile system, though just what is in such a system has not been officially defined.

Construction work on the Red Line toward Glenmont, meanwhile, will continue as scheduled.

About $23 million is programmed to cut three access shafts and an underpass on the line north of the Forest Glen station, now largely finished. Service to Wheaton would begin in 1988 and continue to Glenmont in the 1991.

Work on the Red Line to Shady Grove, scheduled to open in 1984, the Yellow Line's Gallery Place-Pentagon segment and track from National Airport to Huntington, both scheduled to open next year, will not be affected by the law because they were fully funded in previous years.