The New Zealand Government is considering buying four Boeing P-8A Poseidon maritime patrol planes from the United States, which could cost up to US$1.4 billion (NZ$2.03 billion)

However, the New Zealand Defence Force says the price is likely to be less than that.

The Defense Security Cooperation Agency (DSCA) in the United States has released details of the "potential sale" of up to four Boeing P-8A Poseidon maritime patrol planes.

Derek Flynn/Fairfax NZ A RNZAF P-3K2 Orion aircraft at RNZAF Base Woodbourne.

The DSCA said the New Zealand Government intended to use the planes to replace its retiring P-3 maritime patrol fleet.

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"This proposed sale will enhance the foreign policy and national security of the United States by strengthening the security of a major Non-NATO ally which has been, and continues to be, an important force for political stability within the region," the DSCA said.

A NZDF spokesman said the government was considering options to replace the its P-3 Orion fleet, and a letter of offer and acceptance was part of the process.

It was non-binding, and did not mean the Government had committed to buying the aircraft.

The cost indicated was a "not-to-exceed price", and higher than the Defence Force expected to pay.

Any decisions about what the next steps might be in purchasing the planes would be made over the next couple of months.

According to the Boeing website the planes are designed for "long-range anti-submarine warfare, anti-surface warfare, and intelligence, surveillance and reconnaissance missions".

The proposed sale of the equipment would not alter the basic military balance in the region, the DSCA added.

It was also revealed that Australia is looking to spend up to US$137.6 million on anti-radiation missiles, which can detect and jam enemy radar and radio communications.

The tentative order includes 70 high speed anti-radiation missiles, up to 40 advanced anti-radiation guided missiles, and up to 16 captive air training missiles.

Australia would use its purchases as a deterrent to regional threats, and to strengthen its homeland defence, the DSCA said.