WASHINGTON - Ongoing free trade talks were high on the agenda when Prime Minister John Key spent 40 minutes with United States vice-president Joe Biden early this morning at the White House in Washington.

They talked about the Trans Pacific Partnership eight-party free trade talks, which started in Melbourne last month and which have alarmed the dairy sector in the United States.

Mr Key and Mr Biden also discussed the jointly funded new global alliance on agricultural greenhouse research, the US economy, New Zealand's contribution to Afghanistan, as well as the Nuclear Security Summit that begins this afternoon, and Iran's nuclear capability.

Speaking to reporters afterwards, Mr Key said he said he understood the "challenges" that a big free trade agreement posed for some, but he made the point to Mr Biden that there were opportunities for the United States, not just New Zealand.

"If you look at the United States it is broadly speaking our second largest market but two-way trade is quite equal. Even from an agricultural perspective we are large importer or agricultural products into New Zealand so it is not a one-way street."

And New Zealand's Fonterra also had a commercial relationship with Dairy Farmers of America marketing cooperative. And the New Zealand dairy industry represented only two per cent of world trade in dairy products.

Almost a third of the US Senate expressed concerns in a letter to United State Trade Representative Ron Kirk about opening up the US to the New Zealand industry under any TPP agreement

Mr Key said that when he talked to Mr Kirk at the Apec meeting in Singapore last November, Mr Kirk reminded him that for every international visit he would be making, he would also be making a visit to a state in American "where there is likely to be push-back from an advancing trade agenda -we all acknowledge that."

"But over time we will obviously be getting our message out there that there are real win-wins for both countries if we can advance trade agreements. It is something that is incumbent not just on the United States Administration but on the New Zealand Administration."

Mr Key said the Administration was very serious about reducing and eventually eliminating nuclear weapons.

Mr Biden thought New Zealand could play a "leadership role working with other countries demonstrating that the world free of nuclear weapons could be a better place."

Mr Key described New Zealand a "non-aligned country" and said the United States saw its role as important.

"We are clearly a country that has got a strong history in this area and that could be used a longterm actually to sway international opinion."

Mr Key said the longterm ambitions of the Obama Adminstraiton were "aligned with New Zealand's position - that is they want to see the world free of nuclear weapons - that has been our position since 1986 and well before that."

"New Zealand has shown it is possible - sure the situation is different and there are difference circumstances but I do believe we could potentially get to a world that is free of nuclear weapons if you can get the buy-in of a whole lot of other countries."

Mr Key said he and Mr Biden talked about New Zealand's contribution to Afghanistan - the SAS is based in Kabul at present and the provincial reconstruction team is working in Bamyan which will be replaced with civilian aid a staged exit.

"If any place is ripe for ultimately handing control fully back to the Afghan people it is Bamyan and he acknowledged that. "

Mr Key said he did not believe US warships would return to New Zealand ports "any time real soon," - something former Prime Minister Sir Geoffrey Palmer said would be desirable.

Mr Key said it was "not of any great consequence" and would be symbolic only.

"I don't think we should let that get in the way of improving the relationship."

In statement after the meeting, Mr Biden said he had thanked Mr Key for his "close co-operation on the NSS agenda and goals," and expressed his appreciation for New Zealand's strong support in Afghanistan.

"The Vice President and Prime Minister Key also discussed how our two countries can cooperate further on regional and global matters and work closely together at the United Nations, including on issues such as Iran. "