The administration is preparing its budget for fiscal l987, due on Capitol Hill soon, against a background of relatively good economic news. In December payroll employment increased by more than 300,000, and unemployment dropped below 7 percent for the first time in this administration. Even with the uncertainties of interpreting Christmas-season employment statistics, these figures augur well for the year ahead.

Lower interest rates and the reduction in the value of the dollar are further cause for optimism, particularly for the latter part of this year and into l987.

The lower interest rates will help to maintain the expansion of spending on housing and on business plant and equipment, while the lower value of the dollar will cause the trade deficit to begin to decline. And because of lags in the response of trade to shifts in the dollar's value, the effect on our imports and exports of the declining dollar will have a larger impact in late l986 and 1987.

For all these reasons, a relatively optimistic outlook now seems justified. The primary danger for the economy, of course, continues to be the massive federal deficit.

Fortunately, even if the administration and Congress were tempted to let another year slide by with no action, the Gramm-Rudman legislation will now make that gamble impossible. In fact, an important implication of the outlook for continued growth is that the Gramm- Rudman requirement will not become moot because of a looming recession. The clause that would scrap the deficit target of $144 billion for fiscal 1987 if a recession were threatening is very unlikely to be invoked.

The president and his economic advisers are going to have to find some $50 billion in deficit reduction for 1987 or risk across-the board cts of that magnitude in spending for defense as well as domestic programs. To meet that target with as little pain as possibe, the administration is toying with a proposal that would result in a sham reduction of the deficit.

Fully one-quarter of the administration's total deficit reduction for 1987 is now scheduled to result from the sale of government assets, including government- owned utility plants and financial assets such as past loans to farmers and students.

The administration claims that the Treasury receipts from these sales will reduce the deficit. At first glance this may seem legitimate. But in actuality these government asset sales would be no different from the sale of more government bonds.

Although government accounting methods would make it look as if federal spending and receipts are in better balance, these asset sales would do nothing to lessen the burden of the deficit. That burden occurs because government borrowing to finance the deficit preempts savings that would otherwise be available for private investment in plant and equipment and in housing construction. The administration's proposed asset sales would preempt private savings every bit as much as a federal sale of new debt of the same value.

There may be a good case for privatizing federal power plants, even though the initial accounting reduction in the deficit is illusory. Private management would have greater incentives for efficiency, and the public as a whole would benefit if subsidized bargain rates for government-operated plants were set aside in favor of market rates. There may also be good reasons for ending many of the current government loan programs. Again, politically favored groups such as farmers and small businesses are subsidized by the taxpayers as a whole.

But while the president might be philosophically inclined to endorse such a permanent ban on these loans, Congress would not be willing to go along. It would be sad if Congress rejected the administration's more trenchant spending cuts while adopting the deceptive but vacuous plan to sell assets.

The only way to redress the imbalance in the government's true accounts is to make genuine reductions in government spending or to reduce consumer spending by raising tax revenue. The longer Congress and the president wait to face up to that reality, the more we impoverish future generations.