Top U.S. officials yesterday warned New Zealand that the island country cannot ban U.S. warships from its ports and remain in ANZUS, the military alliance linking the United States, Australia and New Zealand.

"A military alliance has little meaning without military cooperation . . . . New Zealand can't have it both ways," said Paul Wolfowitz, assistant secretary of state for Asian and Pacific affairs.

"We have only one Navy -- not one conventionally capable navy and one nuclear-capable navy; not one navy to accommodate one country's policy and another navy for the rest of the world," he said, referring to New Zealand's decision last month to permit port visits only by those ships that New Zealand can determine are not nuclear-armed or nuclear-powered.

But, Wolfowitz said, "we're still very much in the phase of working to find a successful resolution, and I think we ought to keep at that for some considerable period of time."

Rep. Stephen J. Solarz (D-N.Y.), chairman of the House Foreign Affairs subcommittee on Asian and Pacific affairs, is drafting a resolution that calls on New Zealand to change its policy on U.S. ships. If the policy is not reversed, the draft says Washington should consult with Australia about terminating the 34-year-old mutual defense treaty with New Zealand but maintaining it with Australia.

In testimony before the subcommittee, Wolfowitz said, it is "counterproductive" to focus on what would happen if an agreement were not reached. Wolfowitz and other administration officials said that no punitive actions, such as economic sanctions, have been taken against New Zealand and that they do not endorse such moves.

The United States maintains that port access is an essential part of the alliance's effectiveness. Washington, for the security of its warships and overall deterrence, does not confirm or deny whether its ships are carrying nuclear arms. New Zealand contends that accepting U.S. warships carrying nuclear weapons would make the country a target for a nuclear attack. It has offered to increase its nonnuclear military activities in the Pacific to compensate for withdrawing from nuclear-weapons arrangements with the United States.

As a result of the New Zealand decision, the United States has drastically cut military cooperation and intelligence-sharing with New Zealand; the annual ANZUS council meeting scheduled for this summer has been postponed; and for all practical purposes the treaty is no longer in effect.

Wolfowitz and James A. Kelly, deputy assistant secretary of defense, emphasized the impact of New Zealand's decision on other allied governments pressured by antinuclear movements not to cooperate with the United States in activities involving nuclear arms.

"Whatever the real or perceived risks of alliance defense cooperation, those risks are minimal compared to the dangers associated with a decay in the perceived will of western nations to support one another," Kelly said.

Wolfowitz said the question of whether to follow New Zealand was raised in the Norwegian parliament but was promptly rejected by Norway's defense minister.

[Meanwhile, New Zealand Prime Minister David Lange said U.S. curtailment of defense ties to New Zealand could cost his nation more than $100 million in military expenses, United Press International reported.]