SUDDENLY SOMETHING new -- and bad -- has been added to the Metro route map: where you used to see at least 89.5 miles of the full 103-mile network carefully agreed to and in place, you will now see the forked tongue of a White House transit official. The same administration that last month was said to have "agreed in principle" to construction plans worked out and submitted by representatives from all over this region now says it has agreed with some Senate Republicans to cut federal funds for Metro construction by 25 percent. So much for any commitment by the White House; and that's some thanks for the region's willingness to work with the administration early on budget cuts and an orderly construction plan.

Only weeks ago, the adminstration was recommending allocating $250 million annually for Metro over the next four years -- much less than Metro had sought, but nevertheless agreed to and worked into the 89.5-mile plan. But on Thursday, Ralph L. Stanley, the administration's mass transit chief, told a Senate subcommittee about the 25 percent cut in federal funds. It's all part of the total federal budget compromise, Mr. Stanley said, which means that if "significant changes are made elsewhere in the package, the transit portion would be jeopardized."

Everyone connected with Metro believed that the region's early willingness to work out a budget reduction for the system made sense and would hold firm. Republicans as well as Democrats in both the Senate and House -- including Virginia's Sen. John Warner and Rep. Frank Wolf -- understand both the history of this project and its national as well as regional importance. It is not a gold- plated toy for D.C. locals to ride around in, nor is it just another item on a list of federal transit projects.

Until now, every administration since that of Dwight Eisenhower has supported completion of this model transportation system for all the world to see and use -- and for the taxpayers of this region to pay for in significant ways as well. It should not be forgotten that the fares paid by riders are covering 50 percent of the operating costs, with the rest increasingly paid by the participating state and local governments.

There is no question that the region should further strengthen its commitment to come up with financing for the operating costs in the future. But state and local officials -- anywhere -- should be able to make efficient construction decisions on the assumption that an administration's commitment is a commitment.