Prime Minister John Key was tonight preparing to present New Zealand's case for a free trade agreement at meetings with US Vice-President Joe Biden and Agriculture Secretary Tom Vilsack on the eve of a 47-nation nuclear security summit in Washington DC.
Mr Key was due to meet Mr Biden in the White House about midnight (NZT) followed by a formal lunch with Mr Vilsack.
Acting Prime Minister Bill English today described the meetings as "a pretty special opportunity" to advance New Zealand's trade interests.
"The practical negotiations have just got started and of course negotiating any trade deal with the US is going to be a complex job requiring persistence, so the prime minister is taking the opportunity to push our case every chance he can," Mr English said.
Talks started last month in Melbourne on a Trans-Pacific Partnership (TPP) which would extend the previously negotiated P4 trade agreement between New Zealand, Brunei, Chile and Singapore to include the US, Australia, Peru and Vietnam.
One of the issues Mr Key is expected to deal with when he meets Mr Vilsack is the protest by a group of 30 US senators who have accused the New Zealand dairy industry of "anti-competitive practices".
In a letter to Trade Representative Ron Kirk they have claimed Fonterra wields extensive control over world prices and have asked for their concerns to be given "very careful attention" when the US considers opening up trade with New Zealand.
Trade Minister Tim Groser has described their stance as "palpable nonsense" because Fonterra competes internationally like any other company.
"It's a very, very politicised argument, trying to suggest that somehow New Zealand doesn't play it fair when any person who looked at it objectively would reach exactly the opposite conclusion," he said.
The full sessions of the nuclear security summit, called by President Barack Obama, begin on Wednesday. Mr Key is attending at the personal invitation of the president.
President Obama's goal at the two-day summit is an international agreement to secure vulnerable nuclear material within four years and to take specific steps to crack down on nuclear smuggling.
"The central focus of this nuclear summit is the fact that the single biggest threat to US security -- both short-term, medium-term and long-term -- would be the possibility of a terrorist organisation obtaining a nuclear weapon," President Obama said today.
"We know that organisations like al Qaeda are in the process of trying to secure a nuclear weapon -- a weapon of mass destruction that they have no compunction at using."
Nuclear non-proliferation experts have said there are no known instances of terrorist groups obtaining highly enriched uranium or plutonium that could be used to make a crude nuclear bomb, but note there have been 18 cases of nuclear material being stolen or going missing since the early 1990s.