"The question is 'how long will it take before there's one million?" he asked of annual Chinese visitor arrivals. "I would have thought within about three to four years there will be one million tourists from China alone," he said.
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Tourism New Zealand says China is New Zealand's second largest visitor market.
"Its growing middle-class has seen sustained growth in Chinese visitor arrivals to New Zealand over the last five years. Increased air capacity from the two direct carriers, China Southern Airlines and Air New Zealand - with new players Air China and China Eastern also establishing year-round services in 2015 - has helped this trend," Tourism NZ says.
Key was with a businesswoman said to be China's wealthiest to turn the first sod at the site of the new hotel.
Madam Chan Laiwa, founder of Chinese real estate business Fu Wah, visited the Halsey St site in the Wynyard Quarter/Viaduct Harbour area, opposite ASB North Wharf.
She accompanied Key into the marquee to the call of a kaikaranga.
See an animated flythrough from Panuku Development Auckland showing future plans for the Wynyard Quarter:
See this Google Map showing the site of the new hotel: