BECAUSE WASHINGTON'S subway system has been built on a foundation of crises, the sounding of any financial alarm at Metro has a familiar ring to it. But those scares of yore -- and they were pretty scary -- had to do mostly with the federal government's willingness to shell out for the system. They were perils that pretty much kept Metro's alliance of District, Maryland and Virginia jurisdictions busy battling common enemies. But now, having won the blessing of six presidents and some solid money commitments from Congress, Metro rail construction faces what could be its toughest test of all: without special attention from Govs. Dalton and Hughes and Mayor Barry, the state-regional alliance could come unglued -- wrecking construction schedules.

Tight money and nerves to match have increased the distrust among partners. It's round-robin anxiety:

Maryland officials look at all the subway lines being built in Virginia and threaten to oppose any long-range construction plan unless Virginia swears to keep putting its shares in the pot after its segments have been built.

In Virginia, where the governor and the legislature did come up with taxes to help cover operating expenses of Metro, officials point out that construction money is another matter -- if bonds have to be issued, that requires voter referendums in Arlington and Fairfax counties. But here, too, Fairfax officials see all those lines serving Arlington and become anxious about their own routes.

Prince George's County, meanwhile, sees lines being built in Virginia and Montgomery County and worries too.

The District, which already has kicked in a large amount of money from unbuilt highway projects, has a lot of subway operating, but still has key routes to be built to serve Northeast and Anacostia.

Add to all this the periodic stop-I-want-to-get-off mutterings from county chiefs John F. Herrity in Fairfax and Walter Frankland in Arlington, plus the politicking over bus routes and costs, which is related, and you have the makings of serious trouble. This time, Uncle Sam won't be dashing in for the rescue; the federal govvernment has done its part.

But the collapse of the alliance doesn't have to happen. The anxieties that threaten to play hell with the partnership can be dispelled. We strongly urge Mayor Barry, Gov. Hughes and Gov. Dalton to hold a Metro "sumit" to 1) reaffirm their commitment to a subway construction schedule as well as the payments to meet it and 2) agree on ways to work with top state and county officials as well as the legislatures to enact any measures necessary to permit long-range guarantees of construction money. There is no magic to such a summit -- but it could do an enormous amount of good by removing unnecessary tensions and producing a plan that will put Metro's tracks where they are wanted and expected throughout the region.