WELLINGTON: Concerns are mounting in New Zealand as the Cook Islands’ Prime Minister travels to China this week to sign agreements without properly consulting with New Zealand, despite the two nations' constitutional ties.

New Zealand has become increasingly concerned about China’s growing presence in the Pacific region and the threats it poses to the country’s national security.

Prime Minister Christopher Luxon said on Monday at a press conference New Zealand expected transparency and consultation with Cook Islands after its prime minister, Mark Brown, flagged he was heading to China seeking a partnership in national development including infrastructure, trade and the economy.

The Cook Islands is a self-governing country in free association with New Zealand which provides budget support and commits to defend the South Pacific nation whose people are New Zealand citizens.

"Under our constitutional arrangements, we expect, you know, in matters of defence and security to be transparently discussed between partners. That's all we're asking for here," Luxon said.

He added that once New Zealand knew what was in the agreement, the government would decide how to respond.

New Zealand had made repeated requests to the Cook Islands to share or consult on the contents of agreements that Brown plans to sign with China but had not received a proper response, raising significant concern, deputy prime minister Winston Peter's office said in a statement on Sunday.

"To those who suggest that our engagement with China is somehow secretive, I reject that completely," Brown said in a video statement on Cook Islands Television News Facebook page on Friday.

"We have always conducted our international affairs with integrity and transparency. Every agreement we enter into will be in the best interest of the Cook Islands," he said. He did not provide specifics of the agreement.

Cook Islanders have also questioned secrecy around the agreement. Tina Browne, leader of the opposition Democratic party told New Zealand based radio station 531pn that people were concerned about the lack of consultation firstly about the Cook Islands' passportand not the agreement with China.

“If there is nothing to hide, why are we not consulting with New Zealand?” Browne said.