LAST SUMMER, because of strong congressional and international reaction, the administration appeared to relax its efforts to weaken population-control aid for developing countries. In recent months, however, the Agency for International Development has begun applying rules that could seriously disrupt the network of family-planning programs carefully built up in Third World countries over the last 20 years.

The new rules, being put into effect without congressional approval, go far beyond the law governing AID programs -- in fact, they could not be constitutionally applied to organizations within this country. They would stop U.S. aid from flowing to private foreign organizations -- such as hospitals, clinics or medical schools -- if, using money from private sources or their own governments, these institutions provided information on abortions or performed abortions except to save a woman's life.

Under a longstanding U.S. policy favoring private, voluntary family-planning programs over possibly coercive government-run programs, these private institutions are the major source of family- planning assistance in most of the developing world. Since 70 percent of the population eligible to receive U.S. aid lives in countries where abortion is legal on a wider basis, the rule would have far-reaching implications. Already AID has terminated a long-term grant to the International Planned Parenthood Federation -- the major operator of family-planning programs in many countries -- and frozen a still larger grant to the U.N. population agency.

AID insists that the rules are not meant to impede family-planning programs abroad, only to discourage abortions. But federal law has long forbidden the use of any U.S. foreign aid for abortion or abortion-related activities. And international family-planning agencies have instituted strict and often costly administrative procedures to ensure that the law is not violated.

Although AID was wise enough not to apply the new rule directly to foreign governments, many countries are likely to be offended by this attempt to dictate their internal policies. Even if they are not, many will find it hard to retain U.S. aid. These are countries where even rudimentary health services are in short supply and where the demand for birth-control assistance was far from being met. Attempting to create a separate network of family- planning providers -- which, under the strict AID rules must be totally independent of any hospital, university or clinic where abortion-related services or training are provided -- would be a slow if not impossible job. Whatever the administration's motivation in applying this policy, it must accept responsibility for adding suffering to countries where suffering is already an all-too-familiar condition.