THERE SHOULD BE no minimizing the potential significance of what Prime Minister Rajiv Gandhi has done with respect to India's Sikhs. In just the few months since he took over from a mother who was herself assassinated by Sikhs, he has come to a broad agreement with the community whose turn to terror had created the possibility of awful continuing sectarian violence in the pursuit of a secessionist state. Some countries spend years, decades, even longer times, failing to work out the kind of long smoldering, finally exploding ethnic problem that Rajiv Gandhi inherited last year. That he set it as his priority to try to conciliate the Sikhs, and followed through, indicates an impressive measure of leadership.

All over the world aggrieved minorities are in conflict with the leadership of their countries. Governments have four broad choices in dealing with them: ignore them, crush them, toy with them or meet their reasonable demands. Mr. Gandhi took the last course -- not, it may be noted, the course his mother took. He proceeded on the theory that the best way to isolate the extremists is to negotiate with the moderates, who make up the majority. He personally signed a "memorandum of settlement" with Harchand Singh Longowal, head of the principal Sikh party.

The memorandum addresses a range of Sikh grievances arising from the community's clashes with Indian authority, delicate matters of territory and water, the volatile religious and linguistic issues and the basic question of the relationship of the Punjab (currently 54 percent Sikh, 46 percent Hindu) to the federal state. The agreement evidently will soon be put to a necessary and difficult first test in local elections in the Punjab, which is now under New Delhi's military rule.

Will it work? No one familiar with democratic India's ethnic strains, and specifically with the determination of the Sikhs, will underestimate the difficulty of keeping the Indian federal framework intact. No problem -- not even development -- makes harsher demands on any country's political leadership than maintenance of a reasonably stable balance between ethnic assertion and the national prerogative, all this in a context affected by traditional animosities and much recent blood. Terrorists could yet target the principals on either side.

Against the odds, however, Rajiv Gandhi and his Sikh partners are attempting a rare and major act of statesmanship. For their effort they deserve respect.