THE COMMISSIONER of the Immigration and Naturalization Service is on the spot. He is being portrayed as the heavy in a situation that is complicated by competing equities and terrible human problems. A very fragile bargain, crafted after much turmoil in Congress, is being strained, and the time available for finding a solution is running out.

Last year's immigration reform legislation authorized the granting of amnesty to illegal aliens who have been in this country since 1982. The bill, however, contains no specific language about those aliens' close relatives who do not qualify for amnesty in their own right. The basic amnesty provision was extremely controversial; the House passed it by a slim margin of seven votes. And the Senate Judiciary Committee stated in its report that it "is the intent of the Committee that the families of legalized aliens will obtain no special petitioning right by virtue of the legalization. They will be required to 'wait in line' in the same manner as immediate family members of other new resident aliens."

That looks fine on paper and is indeed fair to those would-be immigrants who have obeyed our law and waited -- with their families -- for visas in their home countries. But now, INS is beginning to encounter cases in which one spouse -- or two out of four children in a family -- does not qualify for the benefit and is therefore subject to deportation. This means that the aliens have to return home and wait for 18 months until they can petition for visas as relatives of a permanent resident of the United States. This is a terrible prospect, but Congress is unmoved. On Oct. 7, Sen. John Chafee's proposal to extend amnesty to spouses and minor children was defeated in the Senate 55 to 45. The program expires next May and the senator still hopes to convince his colleagues at least to stop deportations. But for now, it is clear, the ball is in the INS's court.

Commissioner Alan Nelson told a House subcommittee last week that the service will take no action against minor children if both parents have qualified for amnesty. In addition, INS will not move to deport spouses on the basis of information received in the amnesty application process. Finally, Commissioner Nelson promised to use the discretionary powers given by law to the attorney general to suspend deportation of family members if, in individual cases, there are specific humanitarian reasons for doing so. We hope he is generous in using this discretion. Yes, there is merit in holding the line as Congress intended so those awaiting visas outside the country are not displaced. But the reality of breaking up families, even temporarily, is unthinkable. If Congress will not be moved, the INS should have a heart.