This week the Israeli cabinet voted, in a much-publicized decision, to create a national service program for youth that does not serve in the army. It’s a good idea and not entirely a new one, since the option of working for a year or two in some socially useful capacity instead of serving in the Israel Defense Force has been available to religiously observant girls for several decades.

What’s new is that now this option will be made available to other categories of youngsters as well, especially Arabs and ultra-Orthodox Jews. This is what makes the new program both highly promising and highly problematic, since it touches on the two sectors of the Israeli population that are the country’s least integrated and the greatest threats to its long-term stability.

Traditionally, neither ultra-Orthodox Jews nor Arabs have served in the army, in which — in principle, at least — there is universal conscription at the age of 18. Despite being totally different from one another, both groups reflect a similar story. In neither case have they wanted to serve, in neither case has this bothered the army, and in neither case, therefore, has the government made them serve.

Their disinclination to serve is understandable. Both ultra-Orthodox Jews and Israeli Arabs are ideologically anti-Zionist and have a highly ambivalent attitude toward the state of Israel. On the one hand, they do not identify with it psychologically or emotionally; on the other hand, they are its citizens and accept the fact that they must obey its laws. But serving in its army is something else. For the ultra-Orthodox, the military ethos is a foreign one and military service means exposing their youth to a secular institution that they fear would corrupt its faith and morals. For the Arabs, the IDF is a fighting machine aimed against other Arabs who are their brothers. Neither group feels that it itself has any responsibility to defend Israel against its enemies.

From the army’s point of view, all this has been just as well. The sense of connection that Israeli Arabs feel with the Arabs of other countries, and especially, with the Palestinians of the West Bank and Gaza Strip, makes every Arab soldier a potential security risk, even if very few might in fact commit espionage or treason. And as for the ultra-Orthodox, large numbers of draftees from their ranks, with their rigorous ritual needs and total lack of physical preparedness, would be more of a burden than an advantage.

And so, although the Israeli public, most of whose sons and many of whose daughters do serve in the army, has griped, sometimes bitterly, about this unequal situation, especially in regard to the ultra-Orthodox, no Israeli government has ever wished to make a political issue of it. Apart from the Druze community, which has a history and character of its own, Israeli law exempts all Arabs from military service. (A small number of Israeli Arabs, mostly Bedouins, have volunteered over the years.) In the case of ultra-Orthodox Jews, a different solution has been found, one granting an exemption to every young man registered as a student in a yeshiva. This has been a great boon to yeshiva enrollments, which are close to 100% in the ages eligible for conscription. But this situation can’t go on indefinitely. Because their birthrates are far higher than that of the ordinary Israeli Jewish population, ultra-Orthodox Jews and Israeli Arabs are becoming a steadily larger part of the country’s population. Already today they comprise, between them, more than 25% of all Israelis, and in the younger age cohorts this percentage is far higher. The question of their economic, political, and educational integration into the nation’s life becomes more pressing from year to year. One can say without fear of exaggeration that unless they are integrated well beyond their present level, Israel’s future will be as jeopardized as much as it is by its external enemies. No country can prosper, or perhaps even survive, if a third or more of its population does not identify with it and its institutions.

A program of national service in which ultra-Orthodox and Arab youngsters can get out of their homes, mix with other Israelis, and work for the benefit of their country in a kind of internal peace corps without having to don army uniforms, and can in exchange get some of the financial and educational benefits that soldiers are awarded upon finishing their compulsory service, could be one such institution. But to become that it will eventually have to expand beyond the modest beginnings that now are planned for it, which call for its establishment on a purely voluntary basis. Unless it is made compulsory, just as army service is, it will be availed of by relatively few youngsters and will do little to make the ultra-Orthodox and Arab communities more part of the national fabric or to give other Israelis the feeling that they are pulling their share of the load.

A comprehensive program of national service is only one of many steps that need to be taken in order to enable ultra-Orthodox Jews and Israeli Arabs to feel more Israeli and to contribute more to the nation’s life, and this week’s cabinet decision is only a step toward taking that step. Moreover, it’s politically painless. As long as national service remains voluntary, even ultra-Orthodox and Arab politicians who suspect that it’s really all a Zionist plot to steal their youth away can’t find a great deal to protest about. They’ll squawk loudly, though, if national service ever becomes an obligation for whoever doesn’t serve in the IDF. It’s important that future Israeli governments not back away from that fight.

Mr. Halkin is a contributing editor of The New York Sun.