The United States says it would be open to having troops based in New Zealand if that was acceptable to the New Zealand Government.

Speaking on TVNZ's Q+A programme, US Defence Secretary Leon Panetta said his country was keen to help New Zealand improve its defence capability.

Mr Panetta said having American troops based here could be part of that.

"If New Zealand feels that that's something that they would support and want, we certainly are more than ready to engage them in that kind of relationship. I think it would be very helpful; we do exercises together.

"My approach to this as Secretary of Defence is, whatever we can do to try to help New Zealand develop its capabilities and build a stronger friendship, I'm prepared to do."

Mr Panetta said if New Zealand's defence capability is improved, it will be better for security in the Asia-Pacific region.

The US Defence Secretary announced during his visit to New Zealand that America had lifted a ban on New Zealand Defence Force vessels visiting American ports, further thawing relations after a 26-year stand-off on nuclear issues.

Mr Panetta met Prime Minister John Key and Defence Minister Jonathan Coleman during his brief visit, the first in 30 years by the most senior person in the Pentagon.