New Zealand Trade Minister Phil Goff said today that everything could be up for negotiation in upcoming trade talks with the United States.

The United States formally announced yesterday it will start trade negotiations with Brunei, Chile, New Zealand and Singapore --all members of what is known as the P4 trade agreement.

Goff warmly welcomed the announcement by the United States of its decision to enter into comprehensive Free Trade Agreement (FTA) negotiations to become a full partner to the Trans-Pacific Partnership (P4).

"The announcement is of huge significance and benefit for New Zealand," Goff said.

While the talks will be based on the existing P4 agreement, Goff said the United States will be free to raise any issues of interest.

Prime Minister Helen Clark put the potential deal in the same ballpark as getting a bilateral free trade agreement with the U.S., something the government has sought unsuccessfully for several years.

"I think the value to New Zealand of the United States coming into a transpacific agreement as a partner would be of the same value as we would hope to get from a bilateral FTA," Clark said. "It's very, very big news."

National Party trade spokesperson Tim Groser says it's taken 10 years to get to this point, but it's good news that talks will finally begin.

The Employers & Manufacturers Association said 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 United States would be worth 1 billion NZ dollars (US$680 million) 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.

New Zealand's Council of Trade Unions said free trade talks with the United States pose a risk to parts of the New Zealand economy.