New Zealand Trade Minister Phil Goff says everything could be up for negotiation in forthcoming trade talks with the United States.
The US formally announced on Monday that it will start trade negotiations with Brunei, Chile, New Zealand and Singapore - all members of what is known as the P4 trade agreement.
While the talks will be based on the existing P4 agreement, Mr Goff says the US will be free to raise any issues of interest.
National Party trade spokesperson Tim Groser says it has taken 10 years to get to this point, but it's good news that talks will finally begin.
Radio New Zealand's political editor says other countries - possibly including Australia, Peru and Vietnam - are also expected to join the agreement if a deal is finally reached.
The Employers & Manufacturers Association says it would be New Zealand's most important trade agreement since the Closer Economic Relations deal with Australia in 1983, which phased out trans-Tasman tariffs.
Association chief executive Alasdair Thompson says the talks with the US could be worth $1 billion a year to the New Zealand economy.
It caps a year of breakthroughs in trade talks for New Zealand, after trade agreements were signed with China and ASEAN nations. Exploratory negotiations have also begun with Japan and South Korea.
The Trade Minister Phil Goff says that has been a driving force behind the P4, but there will also be immediate benefits for all countries in the agreement once a deal is reached with the US.
The Council of Trade Unions says free-trade talks with the US pose a risk to parts of the New Zealand economy.
It says New Zealand would face pressure to scrap the state drug-buying agency Pharmac, which threatens big drug companies by keeping prices down.
Council economist Peter Conway says the US would also want laws relaxed on foreign investment and overseas ownership of strategic assets.