Secretary of State George P. Shultz said today that the United States and its allies must "fight back" against international terrorists, their supporters and those who offer them safekeeping, and suggested that the antiterrorist struggle has become an alliance responsibility.

Shultz, in an address at the East-West Center, a nonprofit educational and research institution here, also criticized New Zealand in his strongest language to date for "walking off the job" of alliance duty in February by refusing to accept port calls by U.S. warships unless it received assurances that they were not carrying nuclear weapons.

State Department officials said Shultz's address, which capped a two-week trip to Southeast Asia and the Pacific, was a major effort to define the nature and responsibilities of the alliance structure, a keystone of U.S. foreign and defense policy since World War II.

Shultz took the occasion in the context of alliance duties to make his strongest call for antiterrorism action since the hijacking of Trans World Airlines Flight 847 to Beirut last month.

Speaking of "the international terrorist network," he said, "We cannot allow the enemies of our way of life to attack each ally one by one in the hope that we will be divided and thus incapable of coordinated response."

Shultz pointed out that many U.S. alliance treaties, referring to conventional attacks across international borders, state that "an attack on one ally is an attack on all."

Saying that the threat posed by terrorism is "no less real, no less a form of warfare, no less a direct attack on the interests of the democratic alliance," Shultz implied that the same rule of alliance responsibility to respond should apply to terrorist actions.

"No nation can take refuge in silence or inaction . . . . No nation will be spared," he said.

Shultz, who for more than a year has been calling in unspecific terms for forceful U.S. action against terrorism, did not say exactly what he would do or how alliances could or should be enlisted.

Saying it is necessary to "fight back" rather than "just hold the line" against terrorism, Shultz stated, "We must cooperate to deter and dramatically raise the costs to both the terrorists and those who support them and offer safe haven to them."

In response to a question following his address, Shultz said that despite his determination to "raise the costs" to terrorists, "your government is not about to engage in any sort of gross activity that has the chance of major harm to innocent individuals."

He added, however, that "a person who harbors a terrorist is not an innocent person even though that person has not directly perpetrated a terrorist act."

Much of Shultz's speech dealt with the responsibility of each alliance member to maintain the common defense.

The only ally singled out for criticism was New Zealand, which refused to accept a port call by a U.S. warship in February because it could not be certain the ship was not carrying nuclear weapons.

Under a longstanding policy, the United States refuses to reveal whether nuclear weapons are on board its warships.

Shultz said New Zealand had "added a new element of risk and uncertainty" and had "weakened regional stability" by its condition on accepting U.S. warships.

Despite the cancellation of nearly all U.S. military cooperation with New Zealand, Shultz said "we have left the door open" to improved relations, evidently by New Zealand changing its policy.

New Zealand Prime Minister David Lange said today he would talk with U.S. officials before introducing legislation supporting his government's ban on port calls by nuclear-powered and -armed warships, United Press International reported from Wellington, New Zealand.

Such legislation "must be seen to be in no sense anti-American," said Lange, who has been under pressure at home to honor a promise to legally ban such port calls.