New Zealand said it had reached a deal on Monday to amend its free trade agreement with China - a process that has been going on for years.

The upgraded agreement will facilitate exports to China and reduce the cost of New Zealand's export compliance by millions of dollars each year, the Ministry of Trade said in a statement.

Products coming from New Zealand will get faster entry into mainland Chinese markets, while taxes on different kinds of paper and wood products will be trimmed down under a new agreement with China.

The move will mean that over the next ten years, it said, almost all of New Zealand's wood and paper exports to China will have preferential access.

"This ensures that our upgraded free trade agreement remains the best China has with any country," said Prime Minister Jacinda Ardern in a statement issued at the East Asia Summit following her bilateral meeting with Chinese Prime Minister Li Keqiang in Thailand.

The upgrade secures Beijing's commitment to promoting environmental protection and ensuring that environmental standards are not used for commercial protectionist purposes, the statement added.

New Zealand was the first country in 2008 to sign a free trade agreement with China. For the last three years, it has collaborated with Beijing to upgrade the agreement.

China is New Zealand's largest commercial ally, with around $32 billion New Zealand dollars ($20 billion) in a total two-way business deal.

The partnership hit a roadblock under the coalition administration of Ardern after opposing China's loan borrowing to the Pacific and junking a proposition to invite Chinese telecommunications company Huawei to invest in the proposed 5G network of the nation.

After Ardern's visit to China earlier this year, however, their relations improved. When Ardern made her opening remarks on the new deal during a bilateral meeting with China, the surprisingly enthusiastic Li interrupted, stating: "New Zealand has a competitive edge in many ways and you have a surplus with us, we're happy to have fair trade with you, equal competitiveness with you."

New Zealand has pointed out that in this transformation, existing conditions on dairy trading have been maintained, with all safeguard taxes to be abolished for a good number of products within just under two years and for milk powder for four years.

The next key measures entail a legal assessment of the draft document, the statement said, with the report set to be approved and published by early next year.