With Donald Trump's presidency creating extra challenges for the rest of the world, questions have been raised over what a small country like New Zealand can do for extra protection.

Political commentator and former parliamentary staffer for the National Party David Farrar wrote an opinion piece claiming New Zealand should take up the 125-year-old invitation to become part of Australia.

Farrar says the world has turned into a 'might-is-right' environment since Trump took office and that New Zealand needs to get bigger.

"We're lucky, because we've got a country which we're very, very close to, we're culturally similar to, we're economically integrated to, and we'd be a lot safer if we're a bigger country."

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