The North Atlantic Treaty Organization reaffirmed today its commitment to the deployment of U.S. nuclear missiles in five European countries, but for the first time formally recognized as "a possible option" the scrapping of the plans in exchange for a removal of Soviet missiles aimed at Europe.

The language embracing this "zero-level" option was inserted into the final communique of a two-day meeting of NATO defense ministers here by several European ministers who, under pressure from domestic protest movements, overrode the objections of U.S. Defense Secretary Caspar W. Weinberger.

Opponents of nuclear weapons have shown increasing strength in Western Europe, and several of the NATO ministers reportedly argued during closed-door meetings that the Europeans needed a high-profile response to assuage this opposition, which recently has staged large demonstrations in West Germany, the Netherlands, and other nations.

Acting Defense Minister Hans van Mierlo of the Netherlands and Defense Minister Hans Apel of West Germany are said to have taken the lead in pushing through the policy shift during sessions held at a golf resort hotel here in the Highlands.

Van Mierlo said in an interview today that getting the alliance to acknowledge the possibility of reducing theater nuclear weapons to the "zero level" was a breakthrough for European countries.

"I'm very happy it's in the communique because it is a political goal now set down formally by the alliance," van Mierlo said. The Dutch defense minister described the goal as the "zero option," which he said was not defined in the communique so that arms-control negotiators would have maximum latitude to reach an agreement on reducing theater nuclear weapons in Europe.

Some Europeans have defined the zero option as one that would require the Soviet Union to remove SS20 nuclear missiles targeted on NATO nations in exchange for the United States foregoing its planned deployment of new nuclear cruise and battlefield missiles in Europe.

A high U.S. defense official confirmed tonight that the United States had opposed the "zero-level" language in the communique and doubted that President Reagan would accept anything less than the removal of all 750 of the SS20s, and some other tactical nuclear weapons as well, in exchange for the United States canceling its own deployment plan.

The current U.S. plan, reconfirmed by the NATO ministers today but not yet approved in final form, dates from December 1979 and would deploy 572 Pershing II and cruise nuclear weapons in West Germany, Italy, Great Britain, Belgium and the Netherlands beginning in 1983.

The agreement by the ministers on the potential amendment of that policy came during a conference buffeted by negative European reaction to President Reagan's assertion that he could envision a nuclear war limited to Europe. Weinberger was forced to devote part of the meeting to assuring his counterparts that U.S. nuclear policy had not changed.

Van Mierlo said that he and other defense ministers contended in the sessions yesterday and today that the alliance must respond to the desire to rid Europe of nuclear weapons.

"We see ourselves as suppliers of security," van Mierlo said of NATO defense ministers. "But we often forget that we are supposed to respond to the wishes of the people.

"It's important that the Europeans see that we are striving for their goal," the Dutch defense minister continued. "Then if that goal is not reached, it won't be because we didn't try."

Van Mierlo said that he and Apel used those arguments in the closed sessions, but that Weinberger objected to recognizing the zero option officially on two counts.

"He said it would create the illusion that you could make it come true," van Mierlo said of Weinberger's stand, "and that it is not good for our negotiating position" with the Soviets. The United States is scheduled to discuss tactical nuclear arms in Europe with the Soviets in Geneva on Nov. 30.

A U.S. defense official, who could not be identified under the ground rules of the briefing for reporters, predicted that the Soviets at those negotiations will try to exploit the "zero option" opening.

This is what the communique said in that regard:

"Ministers fully supported the United States commitment to achieve equitable and verifiable agreements, within the SALT framework, on theater nuclear forces at the lowest attainable levels. On the basis of reciprocity the zero level remains a possible option under ideal circumstances. They called on the Soviet Union to live up to the pledge 'to spare no effort to reach an appropriate agreement.' "

Van Mierlo said that the fact the language was included in the communique, despite Weinberger's objections, demonstrated to him that the United States "now is much more prepared to listen to Europe and to respond in a positive way."

Asked if the recent demonstrations in Europe helped push the "zero level" language through this 30th meeting of the NATO Nuclear Planning Group, van Mierlo paused and then tried to draw a fine distinction. He said it was not the demonstrations that propelled the new policy, but the fears that inspired the protests. With a smile, he added: "That's the good of demonstrations."