New Zealand Prime Minister John Key has given strong backing to the Trans Pacific Partnership free trade agreement during his visit to Australia.
Mr Key told business leaders and MPs on Friday he believed the deal would significantly boost New Zealand's economy.
"If you want my view, you see a lot of things in the newspapers, particularly in New Zealand ... you see a reasonable amount of negative comment about the TPP," Mr Key said.
"I don't buy into that. From New Zealand's point of view we think the modelling shows (it's worth) between two and four billion (dollars) to the economy.
"For New Zealand and Australia, I think we should get behind TPP."
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The TPP has faced significant opposition in recent times.
It began as an obscure 2006 deal between Brunei, Chile, New Zealand and Singapore seeking to enhance trade and investment among the partner countries.
But since then Australia, the US, Canada, Japan, Malaysia, Mexico, Peru and Vietnam have joined negotiations for an ambitious expanded deal.
The Australia Institute claims the TPP risks an explosion in the cost of medicines, less Australian television content and relaxed labelling of genetically modified foods.
"The TPP trade deal could have significant, wide-ranging implications for Australian consumers, yet we are being kept in the dark by the government," the institute's executive director Dr Richard Denniss said in a statement on Wednesday.
In the US, President Barack Obama has also faced opposition to the deal within congress.
Mr Obama in his state of the union urged lawmakers to pass laws that will expedite a vote on the TPP.
