OUT ON THE firing lines where government services are provided daily to millions of citizens, it's beginning to sink in that hard times are ahead. This week several hundred state and local officials from agencies providing help to the elderly are gathering in Washington to assess their losses from the budget cuts and plan for a leaner future.

Help for the olderly now comes from many sources. The core money for service programs provided by the Older Americans Act is not threatened by the Reagan budget cuts and, in fact, will increase slightly. State and local governments, however, supplement that money with much oarger funds from other federal programs that provide such things as meals and home care for shut-ins, transportation, legal aid, housing and medical and institutional care. These programs will lose as much as one-third of their purchasing power when dollar cuts and rising prices are taken into account.

None of these losses, however, is as generally threatening to the elderly as an attack on Social Security, the main source of income for about three-fifths of all aged people. The biggest gains against poverty over the last two decades have come among the aged, and improvements in Social Security benefits have been the major factor in those gains. Now, however, with the retirement pary of Social Security moving into a deficit position over the next few years, Medicare headed for financial troubles by the end of the decade and the entire system facing a shortfall sometime in the next century, the idea of cutting back on Social Security has entered the realm of the politically possible.

The question of Social Security's future has been simmering on the back burner for the last few weeks while budget and tax cuts have claimed the Congress' attention. The administration had planned to kick off a new selling campaign for its Social Security proposals with z televised presidential address to the nation -- a decision it has now reversed in light of growing public and congressional opposition to its plan. Congressional enthusiasm for any immediate overhaul, moreover, has been further dampened by a new projection from the Congressional Budget Office confirming that, with some of the cuts already in the budget package, simply allowing borrowing among the three Social Security trust funds would bring the system safely through the next five years.

Although the Senate has rebuffed Democratic attempts to tack the needed inter-fund borrowing authority onto the tax-cut bill, in a year in which Congress is not only preoccupied with the budget and tax legislation but already on the line with its constituents for many other benefit rollbacks, the temptation to leave the problem for another day will be strong. That's not a good idea.

Apary from meeting OMB's budget-cutting targets for 1984, it is true that there is no need for the massive benefit cuts proposed by the administration. But borrowing from the Medicare fund to pay retirement benefits now will only add to Medicare's projected deficit a few years down the road. Without this borrowing, additional revenue or budget savings of about $7 billion to $10 billion a year are needed to provide an adequate cushion. The system, moreover, will remain vulnerable to a continuation of the inflation and slow growth of recent years without some safeguard to keep benefits from outstripping the wage base that supports them. The elderly have a strong claim on the concern of the society, but it is not a claim without some sensible limit.