Thousands of protesters caused traffic chaos in the streets of Auckland on Thursday as trade ministers from 12 Pacific Rim countries, including the United States and Japan, met to sign the Trans-Pacific Partnership (TPP) free trade deal.
The trade pact will see the elimination and reduction of about 18,000 tariffs on the trade of industrial and agricultural goods between Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States and Vietnam.
Opponents claim the agreement undermines domestic sovereignty and are concerned that investor state dispute settlement provisions in the deal could allow corporations to sue governments if they pass legislation that could damage investment prospects.
But New Zealand Prime Minister John Key said the deal set consistent rules to make it easier to do business across the region and was overwhelmingly in the best interests of the countries and their citizens.
"The TPP ultimately represents a giant vote of confidence in and optimism for the future prosperity of our economy and our people."
The signing ceremony took place inside the SkyCity event centre, where trade ministers were isolated from the protests outside the venue.
The event was largely a symbolic one, with the countries involved having two years to ratify the agreement and pass domestic enabling legislation. The agreement will only come into force once six countries, including the US and Japan have ratified it.
US Trade Representative Michael Froman told a news conference in Auckland following the signing that he was confident Congress would approve the deal because of the benefits it would bring to the American economy.
"Members of Congress will see the benefits for their constituents," he said, adding that the benefits have been estimated to be over 130 billion dollars a year in GDP growth and more than 350 billion dollars of additional exports."
Together the 12 countries involved comprise almost 40 per cent of global GDP, encompass a market of more than 800 million people and account for around one-third of world trade.