The nation's trade community got another reminder last week of a looming crisis that just won't go away. The question is whether the nation's leaders even noticed.

The problem, of course, is that the antique computer system at U.S. Customs that processes America's annual $1 trillion in imports is living on borrowed time. It's experienced several brownouts over the past year, and the odds of a major crash get stronger every day.That, in fact, is what occasioned the reminder last week. Customs staged a simulated blackout of its 14-year-old Automated Commercial System at two ports - Charleston, S.C., and Savannah, Ga. - to see what would happen if its personnel had to go back to paper and pen to clear cargo. Final results aren't all in, but the basic finding was what everyone expected, even in a controlled test: The job takes a lot longer without a computer.

In a nation where business depends heavily on just-in-time delivery systems, a nation where trade volume is expected to double during the next 20 years, the increasing likelihood of a major Customs computer shutdown should stir worry. And among traders and Customs people it does. Unfortunately, the concern doesn't go high enough in Washington or wide enough in the country at large.

Neither the Clinton administration nor Congress attaches enough importance to the issue to come up with the funds to replace the old Automated Commercial System with the state-of-the-art Automated Commercial Environment. The administration wants the import industry to pick up the tab, in addition to a processing fee it now pays. The industry says what it already pays would cover the cost if that money weren't funneled into the general treasury. Congress seems skeptical about a new fee, but not interested enough to provide the funds.

So the new ACE computer system remains stalled, and the existing ACS gets older and more inadequate, requiring Customs to spend money on Band-Aid solutions to keep it wheezing along.

Ironically, while Washington focuses intently on the 10-digit cost figure for the new system - currently estimated at $1.2 billion to $1.4 billion over the several years it will take to do the job - it ignores an 11-digit return. Customs uses the computer to collect some $20 billion per year in import duties.

That kind of short-sightedness is shameful, but not surprising. Trade policies can generate a lot of enthusiasm among politicians and bureaucrats. The actual process of trade, however, usually draws little interest and less concern.

Customs has been accused of simulating the crash last week to generate publicity and political pressure. If the test did that, so much the better. But there was a more practical and prudent objective: to prepare for what's inevitable. Data are still being analyzed, but are expected to be reviewed in detail at an agency meeting toward the middle of the month. Officials at each Customs port-of-entry, which customize contingency plans to meet their individual needs, will be encouraged to share the results with their importers and customs brokers. Those business people are anxiously looking forward to the opportunity.

One other fact that's become apparent is that many importers and brokers - and their trade organizations - have yet to put together plans of their own to deal with an ACS crash. That's private-sector myopia. They ought to take a cue from Customs, even as they discuss its contingency preparations, and plan for the worst.

Thanks to Washington's lack of concern, that outcome grows ever more likely.