The United States and Australia put on a display of solidarity here today in the absence of New Zealand, their missing ally in the 31-year-old ANZUS security pact.

Secretary of State George P. Shultz and Australian Foreign Minister William G. Hayden were full of smiles, fellowship and expressions of mutual satisfaction after a day-long series of meetings on security, political and economic issues.

"I miss New Zealand," said Shultz wistfully in a final press conference. Referring to the New Zealand Labor government's refusal to accept port calls by nuclear-powered or nuclear-armed U.S. warships, Shultz added, "We regret that the decision of New Zealand has altered their position in our alliance."

The point of the day's lengthy sessions, which substituted for the annual ANZUS council meeting traditionally involving all three allies, was to show that U.S.-Australian ties remain strong and productive, in a sense demonstrating to New Zealand what it is missing.

Despite the rhetorical emphasis often given to the 1951 Australia-New Zealand-United States treaty, Hayden told reporters that the absence of New Zealand has not affected the security of the region in any critical fashion.

Australian Defense Minister Kim C. Beazley said the absence of New Zealand has imposed additional military requirements on Australia, including additional surveillance and military exercises in the Pacific.

Beazley called these "costs we are prepared to carry" and said that because of U.S. and Australian actions the security of the region is "undiminished."

Asked about New Zealand Prime Minister David Lange's proposal that his government's ban on nuclear-armed and nuclear-powered ships be enacted into law, Shultz said more clearly than before that such action "might precipitate a review of the treaty by the United States."

The U.S. position until now has been that the ANZUS Treaty framework remains intact, even though New Zealand has been excluded from joint military exercises, U.S. intelligence sharing and most other activities, including today's ministerial meetings. But remarks of Shultz and others suggest a more basic reconsideration of the treaty if New Zealand takes legal action as proposed by Lange.

Beyond comment on the legal aspects, Shultz and other U.S. officials steadfastly refused to comment on New Zealand's internal politics, especially the prospect that the Labor Party might be ousted and the warship ban reversed.

The New Zealand Labor Party, which was voted into office at this time last year, has long advocated a ban on nuclear-powered or nuclear-armed ships in the country's ports. In February the government refused to accept the port visit of a U.S. warship because, under longstanding U.S. policy, Washington refused to say whether the ship was armed with nuclear weapons.

A central U.S. objective in dealing with New Zealand was to protect the "no confirm or deny" policy on nuclear arms which facilitates U.S. deployments worldwide. A major concern was that New Zealand's stand might stimulate a "nuclear allergy," prompting other nations to follow suit.

As of today, according to a senior State Department official who briefed reporters, U.S. relationships with other nations in the region have been "basically unaffected" by New Zealand's nuclear-related actions.

A South Pacific nuclear-free zone, which is being proposed by Australia and several other nations, has been drafted in such a way that it is not expected to interfere with U.S. naval deployments or any other major military activity of the United States. Shultz said he found Hayden's explanations of the South Pacific proposal "reassuring." Shultz did not rule out eventual U.S. adherence with the plan if enacted by the nations of the area.

The only setback for the remaining two allies on the nuclear issue today was a last-minute change in the site of the Shultz-Hayden press conference from a spacious room in Parliament House to an inadequate chamber in the Ministry of Foreign Affairs, apparently because organizers feared an antinuclear legislator would make an appearance. The legislator did attend the press conference, anyway, a U.S. official said, but did not make any statement.

The new site was so overcrowded that all print journalists were required to leave before the session could start, with broadcast journalists evicted halfway through to make room for those ousted before.