Protest boats will be banned from parts of Auckland's harbour during a historic visit by a United States warship.

The US Navy is sending the USS Sampson to Auckland for the Royal New Zealand Navy's 75th birthday next month - the first visit by an American ship in 33 years.

Transport Minister Simon Bridges today declared the International Naval Review a Major Maritime Event.

That meant vessels not taking part in the review would have to stay clear of restricted areas in the Waitemata Harbour, Rangitoto Channel and parts of the inner Hauraki Gulf.

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Bridges said the restrictions were intended to "ensure the safety of everyone on the water, including people who are not part of the event".

"Many harbour users will be familiar from previous experience with the way that Auckland Council and event organisers manage the day-to-day conduct of these occasions.

"For example, the relevant legislation was originally put in place prior to the America's Cup."

Bridges did not specifically refer to potential protest. But anti-nuclear groups and peace activists have promised to greet the USS Sampson with a protest flotilla.

Unofficial vessels will have to stay 60 metres away from the naval ships when they are anchored in Aucjland harbour.

Vessels will also have to stay 100 metres away from the sides and back of the navy ships while they are moving, and 500 metres from the front of the ships.

Twelve countries are sending vessels to the Naval Review.

Under New Zealand's anti-nuclear law, the prime minister has to be satisfied that any visiting ship is not nuclear-armed or powered.

Prime Minister John Key granted approval for the US ship's visit after considering advice from the Ministry of Foreign Affairs and Trade.

The law has never required foreign countries to confirm or deny whether their vessels are nuclear armed or powered.

But the US chose not to send any ship as part of the reprisals for the anti-nuclear policy, which effectively suspended New Zealand from the Anzus security alliance in 1985.