New Zealand has agreed to buy four Boeing P-8A Poseidon maritime patrol planes, Defense Minister Ron Mark said Monday, strengthening surveillance capabilities as it works to counter the rise of new powers, such as China.

New Zealand is responsible for patrol and rescue missions in an area of the Pacific Ocean bigger than Europe and plans to step up its engagement in the South Pacific, where it is losing sway over small island nations to China.

Mark said the aircraft were acquired from the United States through its foreign military sales program and would cost 2.34 billion New Zealand dollars ($1.6 billion), including training costs. They would be operational in 2023.