Foreign Minister Murray McCully says the Wellington Declaration signed by US Secretary of State Hillary Clinton is likely to see more military training and exercises with the United States, though some restrictions will remain.
Mrs Clinton is in New Zealand as part of her visit to the Asia-Pacific region and signed the Wellington Declaration with Mr McCully on Thursday.
The declaration formalises a new strategic partnership between the two countries, commits to regular meetings at foreign minister level, working together on trade and holding annual military talks.
Mr McCully told Morning Report there have always been limitations on interactions because of New Zealand's nuclear free legislation.
"It means that while Australia and the United States have an alliance, we don't have one, and we had to try and find a new, positive way of expressing a partnership that wasn't an alliance."
He says they've made it very clear New Zealand makes its own decisions, and has an independent foreign policy.
Mr McCully says changing the military relationship between the two countries has been an incremental process.
"The United States completed a review of the defence relationship and how we could move that partnership forward.
"It's not something that was ever going to result in a single announcement, it was always going to be something that would result in gradual progress - and we're seeing that."
Labour Party leader Phil Goff says he would welcome the chance for New Zealand troops to train more closely with the American military.
Mr Goff says New Zealand must retain an independent foreign policy, and having a working partnership is preferable to an alliance that would bind the country to particular policies.
Mr Goff says the Wellington Declaration is consistent with the strengthening of the relationship over the last 12 years.
Strategic analyst Paul Buchanan says America is re-establishing its relations with New Zealand partly because of its perception of a Chinese threat in the Pacific.
Mr Buchanan, who was formerly with the US Defense Department, says America wants to shore up support in the south Pacific to counterbalance the growing influence of China, which is becoming a naval power.