US Secretary of Defence Leon Panetta (L) shakes hands with New Zealand's Minister of Defence Jonathan Coleman
The US is lifting its ban on New Zealand naval ships in its ports.
The move was announced by Defence Secretary Leon Panetta, who is in New Zealand to discuss ways of improving military co-operation.
He is the first Pentagon chief to visit since New Zealand banned nuclear weapons from its territory in 1985, reports the BBC.
Since then, US warships have been unable to use its ports. Washington suspended its defence treaty with New Zealand in 1986.
Panetta told reporters: "While we acknowledge that our countries continue to have differences of opinion in some limited areas, today we have affirmed that we are embarking on a new course in our relationship that will not let those differences stand in the way of greater engagement on security issues."
The ''policy change'', Panetta said, would make it easier for the military of both countries to ''engage in discussions on security issues and to hold co-operative engagements''.
He was speaking in Auckland at a joint news conference with New Zealand Defence Minister Jonathan Coleman.
Earlier, Coleman said his country welcomed stronger ties, although he said New Zealand's anti-nuclear position remained unchanged.
The relationship between the two countries began thawing after New Zealand sent troops to Afghanistan in 2003.
Panetta also visited Tokyo and Beijing this week as part of a regional tour.
The trip, one of several to the region this year, is seen as central to the US effort to rebalance its forces to the Asia Pacific area as part of a new military strategy.