Special agricultural trade envoy Alistair Polson is heading to Canada on Monday to try to convince North American farmers that their industries should lower their trade barriers and embrace free trade.
He will be lobbying farming leaders in Canada and the United States on the merits of the Trans Pacific Partnership trade negotiations.
Mr Polson says the Canadian dairy industry will be a particularly hard nut to crack.
He will meet the Alberta Cattlemen's Association and has been invited to participate in a discussion about dairy supply management which is protected by very high tariffs and is a stumbling block in the negotiations.
Mr Polson said he will be emphasising how the New Zealand dairy sector has thrived without trade protection.
But with current dairy tariffs of 299% and an industry which staunchly defends that barrier, Mr Polson said the Canadian dairy industry is a challenge for the trade negotiations.
"They've positioned themselves politically so they hold sufficient power to stop their government signing away any of their advantages or their tariffs that protect them and potentially this is a stumbling block for the whole TPP negotiations."