FOR SEVERAL years the country has been going through a series of regional recessions, starting in the Southwest. Now New England is sliding into a decline, and the contagion seems to be heading this way. It can be tracked by delinquent real estate loans, and the federal bank regulators have published figures showing that delinquency rates have been rising faster in this part of the country than anywhere else. That means trouble even for an economy as stable and prosperous as the Washington area's, and in particular it means trouble for the banks that made these loans.

The banking system is not likely to follow the S&L industry into catastrophe. But neither is it in good health. While the number of bank failures nationwide this year is no higher than last year, that number is still very high. Banks have increasingly been putting their depositors' money into real estate loans, and delinquencies in real estate loans have been rising rapidly in many eastern states. The rate of delinquent loans to banks in the District of Columbia is now nearly as high as in Texas and Louisiana, where a recovery is at last underway. While delinquency rates are a good deal lower among the Maryland and Virginia banks, even there they are rising with dismaying speed.

Trouble on this scale, in a region whose economy is as shockproof as any in the country, is a warning of vulnerability. It's another signal that the American banking system, under the present laws and with its present structure, is not well adapted to the financial world that is evolving. In the past week Congress has received two reports of more trouble ahead. Its auditor, the General Accounting Office, observed that banks' loans have been getting riskier, and banks' performance -- measured in losses and delinquencies -- is getting worse. The bank's deposit insurance fund has been losing money steadily since 1987, and the Congressional Budget Office says that this year's losses will be unprecedented. The insurance fund can't be increased even to minimally adequate size, the CBO added, without raising premiums to a level that might push additional banks into failure.

If the economy should now slide into a nationwide recession, the pressures on the banks will rise dramatically. Rather than merely fiddling with changes in deposit insurance, the administration and Congress are going to have to take a much broader view and start thinking about basic ways to buttress and stabilize the whole banking system. While foreign competition is rapidly increasing, the condition of the American banks remains visibly less strong than it needs to be.