Key says he put the FTA upgrade on the agenda when he met President Xi Jinping in Washington DC at the recent nuclear security summit.
"I said to him we have been long-standing friends and this really matters to us," he said. "Secondly, we can't embark on the upgrade without dairy being included. It's 45 per cent of our exports so I can't leave them out."
Key will be looking to Xi to give the Chinese bureaucracy a steer to get the detailed negotiations on the upgrade under way.
Key told the Herald that New Zealand will "trade some stuff" that China also wants. He would not divulge the detail but it appears likely that visa extensions will feature.
Much of the business will be done at Key's Monday meeting with Premier Li Keqiang at the Great Hall of the People. On Tuesday, there will be a subsequent meeting with President Xi Jinping followed by a private dinner.
Other issues likely to feature in the bilateral talks include Chinese foreign direct investment in New Zealand and the length of time it takes potential investors to have applications assessed by the Overseas Investment Office.
Key notes this is also a bugbear for investors from other nations.
"We'll give a bit of reassurance that while the law isn't changing, the efficiency of the process will."
It is expected that detailed discussion of sensitive issues like China's reclamations in the South China Sea may take place during the private dinner with the president.
He will also put in a word for Helen Clark, whose bid to be the United Nations' next Secretary General stepped up in New York this week.
'First son' goes along for the ride
DJ Max Key - dubbed the "first son" by Beijing - will accompany the Prime Minister to China on the air force 757 that leaves Auckland this weekend.
"They are apparently super-excited about the - quote 'first son' unquote - coming," laughed father John Key. "They have got him going to a girls' school."
Key explained that President Xi Jinping had invited him to bring his family with him on his next trip to China.
Max Key's celebrity preceded him when he hit Sydney earlier this year, staying with Key and his wife Bronagh at Australian Prime Minister Malcolm Turnbull's harbourside mansion during an official visit.
He is no stranger to life in the high lane, earlier joining his parents at Balmoral Castle in Scotland as a guest of the Queen, and playing golf with Barack Obama in Hawaii.
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