New Zealand is buying four Boeing P-8A Poseidon maritime patrol planes from the U.S. to replace aging aircraft, Defense Minister Ron Mark said Monday.

The planes will cost 2.35 billion New Zealand dollars ($1.6 billion), including training systems, infrastructure and other associated costs, he said.

It will take delivery of the planes and begin operations from 2023 and will pay for the planes and infrastructure over a number of years.

"Maintaining a maritime patrol capability is essential for New Zealand, for national security and for our ability to contribute to global security efforts," Mark said.

The planes, a modified version of the Boeing 737 commercial airliner, will replace an aging fleet of six P-3 Orions which have been in service since the 1960s, Mark said.

"The purchase enables New Zealand to continue to deploy in a wide range of airborne maritime situations independently and, when required, work with partners including Australia, the United Kingdom and the United States," he said.

New Zealand is responsible for a huge search and rescue area over the Southern Ocean and South Pacific. Wellington also regularly deploys military assets for regional humanitarian relief efforts.

Mark said the Poseidons had a greater speed and range than the aircraft they will replace.

Approximately half of the budget would go towards purchasing the planes, which have state-of-the art radar and high-definition cameras, while the rest would be spent on costs such as infrastructure and flight simulators, Mark said.

The new planes will begin operations in 2023.

The purchase comes just weeks after close neighbor Australia announced plans to invest $5.2 billion to develop and buy high-tech U.S. drones for joint military operations and to monitor waters, including the South China Sea.

They will complement the seven P-8A Poseidon planes Australia currently uses.