The world is on the verge of making history in a big way by making this planet a safer place to live. But much more work will have to be done if the big powers are to complete the long, hard task of beating swords into plowshares.

After 21 months of talks, the 16 members of the North Atlantic Treaty Organization and the six remaining members of the communist Warsaw Pact will meet Monday in Paris to sign an agreement drastically slashing their arsenals of conventional weapons.This pact, scrapping a quarter of a million non-nuclear weapons amassed during four decades of Cold War, is not only the most sweeping and complex agreement in history to reduce weapons arsenals. It is also the first treaty covering conventional arms since World War II - and perhaps the first one ever to be implemented before it was signed. Under growing pressure from Iron Curtain countries rushing to embrace democracy after ousting their communist governments, the Soviet Union was forced to start withdrawing troops and tanks from its former allies even before the arms reduction talks were concluded.

But the achievement so far deserves only two cheers rather than the usual three.

For one thing, though the new pact provides for mutual on-site inspections, the two superpowers still have not ironed out the details of the procedures for verifying that the promised arms reductions actually take place. Also not settled is how much the hard-pressed Soviets will pay to melt down tanks and inspect stockpile reductions.

For another thing, the new pact covers only military hardware, not military manpower - which is to be the subject of talks starting a week after the Paris summit.

For still another, the world won't be as safe as it can and should be until the superpowers follow up pacts curbing conventional weapons and military personnel with one curbing nuclear arms and missiles. On this score, a variety of stumbling blocks remain - including three particularly big ones:

- The kinds of testing and other restrictions to impose on the 154 heavy, ground-based SS-18 intercontinental ballistic missiles the Soviets are to retain under the Strategic Arms Reduction Treaty.

- Whether the Soviet Backfire bomber is to be classified as a strategic weapon, as the United States demands. That would mean counting Backfires against numerical weapons limits established in the treaty.

- The restrictions to be imposed on U.S. and Soviet transfers of weapons barred under the treaty to allies. This issue primarily concerns arms that Washington would like to turn over to Britain outside the treaty's limits.

The new arms control treaty being signed Monday is a foundation to build upon, not a place to rest. Washington can best do so by pursuing the policies and exploiting the realities that achieved the breakthrough to be formalized in Paris.

Keep in mind that progress on arms control is being achieved not because of skilled negotiators but because the United States kept turning a deaf ear to Soviet demands for unilateral concessions and because the demand for freedom behind the Iron Curtain soared as communism failed to make good on its promises of a better life.

The key to continued progress on arms control, then, is to avoid the temptation to start dismantling NATO and to keep America strong economically as well as militarily.