New Zealand Prime Minister John Key has said China is one of New Zealand's vital 21st century partners and New Zealand has set out an ambitious work programme to ensure that the relationship continues to flourish.

Key will pay an official visit to China on July 7-10 and visit the New Zealand Expo Pavilion in Shanghai to mark New Zealand's "National Day" on July 9. It was his second visit to China as prime minister. He visited China in April 2009.

In an interview with Xinhua, Key said: "when I met with (Chinese) Premier Wen Jiabao last year we agreed that the New Zealand-China relationship was at its 'best ever in history'. I am delighted to return to China, my second visit since becoming Prime Minister, and very pleased to have hosted the recent visit by Chinese Vice President Xi Jinping."

"High level attention to this relationship shows how important it is to both countries," he added.

"I am very pleased to have the opportunity to see first hand China's and New Zealand's major investment in Shanghai Expo 2010. New Zealand is taking advantage of the opportunities that Expo creates," he said.

"The Shanghai Expo is a prime opportunity to grow markets for New Zealand goods and services in China, and to capitalize on New Zealand's unique position as the first developed country with an FTA with China," Key said.

"New Zealand's target is for our pavilion to attract 10 percent of the total visitors to Shanghai Expo, so assuming that the overall target of 70 million is achieved, we are aiming for 7 million visitors," he said.

Besides China, Key also visits South Korea and Vietnam during his Asian trip.

Key said Asia is clearly becoming increasingly important to New Zealand. "Strengthening our relationships with the Asian region is a key priority for the Government and this visit will further underline our already warm relationships with these three countries," Key said.