THE STRUGGLE to control the federal budget deficit slipped badly last week, with the agreement brokered by the White House. It is now late in the season to regain momentum for more substantial cuts in the deficit, but it is too early to stop trying. There are better choices to be made than those that the administration has worked out with the congressional leaders so far.

The agreement, as it stands, protects the Senate's figure for defense appropriations as the administration wished. It also protects the cost-of-living increases in Social Security benefits, as the House Democrats wanted. It's a compromise, in the sense that nobody compromised. But they would have done better to go the opposite way -- to take the Senate's position on Social Security and the House's figures for defense appropriations. That would mean eliminating inflation adjustments for both, holding them at their present levels for a year. Sacrificing the inflation adjustments ought not be done for more than one year. Over a longer period, it would impose a dangerous erosion on two crucial functions of government. But for a year, as a badly needed contribution to restraint of a dangerous deficit, it would be not only tolerable but good policy.

It would lift this year's attempt at fiscal control above the recent pattern of alternating complaint and acquiescence, in which the deficit sinks a little in good years but rises a lot in the bad ones. This year, the third year of recovery from the last recession, the deficit will probably be about $215 billion. That's up $30 billion from last year. For next year, both House and Senate have now passed resolutions that, following very different routes, would push it down to $173 billion or a little less. But last week's agreement on defense and Social Security makes it unlikely that they will actually hit that target. There's now a hunt under way for other vulnerable items elsewhere to hold total spending within the resolutions' limits. It's possible to find them -- but it isn't easy to cut a long list of small items and make the cuts stick.

Before ending the hunt and going on holiday, the conferees from the two congressional budget committees, and the White House, need to give more consideration to the unpleasant but necessary alternative -- deletion of inflation increases for the two largest and, in political terms, most sensitive categories in the budget.

Both defense and the pension system are threatened by continuing uncontrolled deficits, for both require a strong and stable economy. A temporary freeze serves the interests of both. And beyond that temporary freeze? Just as a compass needle keeps swinging back to north, all the logic of the budget keeps coming back to one familiar point. It's going to take a tax increase to pay for the services and protections that most Americans -- not only congressmen, but the people who elected them -- consider basic federal responsibilities.