A treaty hangs in limbo down under. Lange takes an economic risk over antinuclear stance

The ANZUS treaty binding Australia, New Zealand, and the United States in a mutual defense pact has been effectively mothballed. But the man whose government's antinuclear stance sparked off the crisis in the South Pacific alliance believes that a lot of fuss is being made about very little.

The New Zealand prime minister, David Lange, defended his country's ban on visits by nuclear-powered and nuclear-armed ships in a debate Friday staged by the Oxford University Union. After winning the debate, he went on to see British Prime Minister Margaret Thatcher at No. 10 Downing Street.

She told him that she totally opposed the ban, but Mr. Lange emerged from the meeting saying that he was not prepared to change his policies, even though hours earlier the Australian prime minister, Robert Hawke, had ``indefinitely postponed'' next July's ANZUS council meeting in Canberra because of the New Zealand nuclear ban.

Against Mr. Hawke's assertion that ANZUS now existed ``in name only,'' the pugnacious and articulate New Zealander said the alliance was not at an end. What had ended, Lange said, was his country's readiness to agree to visits by nuclear ships of any nation.

Lange came to office last July with a landslide majority and a mandate to impose the nuclear ban. The Oxford Union debate pitted him against the American preacher, the Rev. Jerry Falwell, who argued that nuclear weapons were morally defensible and lost the debate.

The New Zealand prime minister, a former Methodist lay preacher, told the Oxford Union that it was imperative to keep the Pacific area nuclear free.

``Rejecting nuclear weapons is to assert what is human over the evil nature of the weapon; it is to restore to humanity the power of decision; it is to allow true moral force to reign supreme,'' he said.

Lange went on to say that he hoped other Pacific region nations would follow the New Zealand example. ``I see no reason why we should be incinerated in our own defense,'' he declared.

The New Zealand leader's passionate contribution to the debate removed any doubt there may have been about his sincerity on the nuclear issue. He has placed it at the center of his government's policies and, despite pressure from New Zealand's US and Australian partners in ANZUS, is determined to keep it there.

At the same time Lange knows that he is running economic risks by sticking to an antinuclear line.

There have been suggestions from within the Reagan administration that the US may make it difficult for New Zealand to go on selling quantities of farm produce in the US.

Before Lange reached London, British officials hinted that the Thatcher government's readiness to argue New Zealand's case for special trade treatment with the European Community (EC) might begin to flag as a direct result of the nuclear-ship ban.

Last month in Washington Mrs. Thatcher heavily criticized Lange, but by the time Lange reached London her rhetoric had become less severe. Whitehall officials said British support for New Zealand in EC would be unaffected.

This is important for Lange, as the New Zealand economy is languishing and external trade in farm produce is one of the few ways the country has of restoring its position.

Behind the scenes Lange was said to be increasingly worried by the adverse reaction in the US, Australia, and Britain to his government's policies. One of his concerns is that the National Party opposition in New Zealand is already making a major issue of the nuclear ban.

If enough New Zealanders begin to waver on the nuclear question, Lange's Labor Party could lose power at the general election scheduled for 1987 -- especially if in the meantime the New Zealand economy could be shown to have been harmed by the ban on nuclear ships.

In Whitehall, Lange tends to be seen as an idealist whose strong views on nuclear weapons may lead him into a politically untenable situation.

At home, Lange insists his views are well understood and supported by a majority.

The Australian prime minister's discouraging remarks about the future of ANZUS obviously disappointed Lange.

In recent years Australia and New Zealand have entered into a cooperative trading agreement and have tried to deepen political consultation.

One effect of the Lange government's nuclear policies is to put the new ``hands across the Tasman Sea'' spirit under heavy strain. New Zealanders already are said to resent a US decision to deny the Lange government intelligence infomation, some of which is gathered via listening stations located on Australian soil.

Lange said in London that he regrets the US denial of intelligence data, but that it would not change his mind about the immorality of nuclear weapons.