Prime Minister John Key says New Zealand's relationship with the United States has "come of age" and he is the "lucky Prime Minister" to have been in the seat when it happened.

He was delighted with his visit to the White House early on Saturday even though it was truncated because of the US debt-ceiling crisis facing President Barack Obama.

He also saw an impressive line-up of Cabinet members responsible for finance, defence, homeland security and trade, as well as meeting Federal Reserve chairman Ben Bernanke and having a top-level intelligence briefing.

"I believe that they want to demonstrate through the seniority of people we saw and the tone of all the meetings how they feel about the relationship, and in some respects I'm the lucky Prime Minister to benefit when the relationship really has come of age, given all the difficulties we've had for the last couple of decades," Mr Key said in a Herald interview shortly before leaving Washington.

He credited previous prime ministers for their efforts, too, in repairing relations after New Zealand's anti-nuclear laws effectively ended the Anzus alliance.

He cited three areas of very close co-operation: trade; the Pacific, where New Zealand, with Australia, was the US's "go-to guy"; and intelligence-sharing under the "Five Eyes" agreement among the US, Canada, Britain, Australia and New Zealand.

Full intelligence sharing was restored in 2009.

The key item on the Washington agenda was trade and the Trans Pacific Partnership among nine countries. "The big game in town is trade, and that is the area we push at every opportunity that we get," Mr Key said.

Citing the reasons doors are now opening and New Zealand is now described as a "strategic partner" of the US, he indicated New Zealand was an ally in achieving America's ambitions on trade in Asia in the context of the rise of China.

"They share our view, from [Treasury] Secretary [Timothy] Geithner through to the President, that there'll be very powerful growth in Asia over the next 10 to 20 years, and I think the Americans know that that's both an economic opportunity and also presents some potential risk for them in terms of leadership in the region if they were to not be engaged in Asia.

"Obviously they are conscious of China, so they are not going to lose the opportunity to be engaged in Asia."

He said the TPP was more than just a matter of trade for the US. "It's an opportunity to make sure they stay very connected."

The Prime Minister said the reason the US wanted New Zealand involved was that our participation would lift the standard of any agreement and encourage others into it.

"I think they see us as the gold standard in terms of trade."

He also said the US believed other parties would be more likely to join a multilateral trade deal if New Zealand were involved.

"We've got a lot of expertise in that area," Mr Key said, "particularly when you think about countries like Vietnam and the like where they don't have as much experience in negotiating FTAs."


'I want to welcome Prime Minister Keys [sic] to the Oval Office. [I] have always been struck by the intelligence and thoughtfulness the Prime Minister brings to his work.'

'We are very pleased that the relationship between NZ and the US is growing stronger by the day.'

'We are still heartbroken by the loss of life and property resulting from the earthquakes in Christchurch and are incredibly impressed by the resilience of the people.'