New Zealand needs to ensure it does not become unhinged over the spat with the Cook Islands, says an international relations specialist at Victoria University of Wellington.

New Zealand expressed renewed concern on Monday about the Cook Islands' prime minister travelling to China this week to sign agreements without properly consulting with Wellington despite the two nations' constitutional ties.

The Cook Islands is hugely reliant on New Zealand under a longstanding "free association" agreement that provides it with defence and financial support. China's growing influence