Contrary to what many Americans seem to think, Uncle Sam does not have bottomless pockets.

That means there are sharp limits to how far Washington can and should go in bailing out a growing list of troubled private and government lenders.There are limits, that is, unless Washington doesn't mind thwarting efforts to eliminate the federal deficit, risking a national taxpayer revolt, and encouraging lenders to persist with the lax practices that helped get them into trouble.

We make this point because the General Accounting Office on Wednesday added the Farmers Home Administration to the list of troubled lenders that may need a federal bailout.

The list already includes the ailing savings and loan industry, which could need $60 billion or more worth of help, plus the Farm Credit System, which got $4 billion only last year.

Even the Federal Deposit Insurance Corp., which insures bank deposits, is said to face greater liabilities than it officially recognizes - though it has more than enough reserves to handle any foreseeable bank failures.

Now the GAO says the Farmers Home Administration, which acts as a lender of last resort to farmers, has run up a deficit of $36 billion. Why? Because the farm economy has been sour for so long. Because the FHA makes loans at lower rates than other lenders would charge. And because many of its borrowers are, by commercial standards, not creditworthy. Though some of the loans are backed by land, others are not - making recovery of the money nearly impossible.

This page has favored efforts to bail out the Farm Credit System and replenish the fund that cushions savings and loan institutions. We have done so because the collapse of those operations would set off a financial chain reaction, ruining much of the rest of the economy and costing far more than the bailouts involved.

But just because federal help is warranted for one part of the federal farm lending system, it doesn't necessarily follow that other parts of it are automatically entitled to such help, too. The Farmers Home Administration's problems should be dealt with strictly on their own merits. Since a collapse of the Farm Credit System would do far more damage than a collapse of the FHA, the FCS should continue to come first.

Moreover, if Congress should somehow decide to ride to the rescue of the FHA, any federal help should be accompanied by reforms and a tightening up of lending practices as was the case with the FCS. That should include a searching look at the quality of the FHA's management.

As it is now, Congress already faces the prospect of having to pare $1.5 billion or more from farm programs next year just to help meet the mandatory targets of the Gramm-Rudman deficit reduction law. Any help to the FHA can only further complicate that effort.