China has postponed a major tourism campaign in New Zealand days before its launch and Prime Minister Jacinda Ardern's visit to Beijing has been further delayed as concerns mount of strained ties over China's growing influence in the Pacific.

Ardern on Tuesday acknowledged there were "complexities" in the relationship with China, but dismissed concerns of a rift with New Zealand's largest trading partner.

"Our relationship with China is a complex relationship and sometimes it will have its challenges," Ardern told TVNZ in an interview.