A group called New Zealand Not for Sale has vowed to fight the Trans Pacific Partnership Agreement (TPPA).
The agreement - to be discussed at the United States New Zealand Partnership Forum in Christchurch on Monday - is intended to free up trade between New Zealand and eight other countries, including the US.
But New Zealand Not for Sale, which held a public meeting attended by about 50 people in Christchurch on Sunday, says the agreement won't benefit New Zealand.
A spokesperson for the group, Murray Horton, says signing it could compromise New Zealand's rights in terms of law and policy-making.
The group's campaign secretary, Christine Dann, says they feel the public doesn't know what the TPPA is about.
PM to give opening address
Dozens of government and business leaders have gathered in Christchurch for the forum.
Prime Minister John Key is giving the opening address to an audience that includes representatives from corporations like Boeing and Time Warner.
Organisers say the meeting will look at ways of building on the Wellington Declaration, an agreement signed last year that committed New Zealand and the US to regular political and military talks.
Council of Trade Unions president Helen Kelly says the push for the TPPA ignores concerns about environmental standards and labour rights.
She is calling for an alternative forum where those concerns can be debated.
