Facing a staggering financial crisis and a stalemate in Washington, the Metropolitan Transportation Authority threatened on Wednesday to adopt a doomsday plan if it did not receive as much as $12 billion in federal aid, including slashing subway and bus service in New York City by 40 percent.

The plan paints a bleak picture for riders: Wait times would increase by eight minutes on the subway and 15 minutes on buses; Long Island Rail Road and Metro-North trains would run at 60- or 120-minute intervals. Upgrades to the subway’s signal systems, which have been the source of many delays, would be scrapped.

The agency is facing a staggering $16.2 billion deficit through 2024, after the coronavirus pandemic wiped out its operating revenue — which comes from fares, tolls and subsidies — virtually overnight. Ridership on the subway, which plummeted by 90 percent in April, has only reached a quarter of usual levels, even as more and more New Yorkers return to work.

The state-run transit agency has requested $12 billion in aid to cover its operating losses through 2021. But after negotiations over the next stimulus package stalled this month, immediate federal support did not appear to be forthcoming.