The Defence Force is brainstorming with local and overseas companies on how to improve intelligence, surveillance and reconnaissance in the oceans around New Zealand.

Its capability plans calls for spending $50- to $100 million over four years on long-range aerial drones.

But the NZDF in a new tender document said drones were just an example and it was open to any solutions for monitoring the South-West Pacific and Southern Ocean.

"The Persistent Surveillance (Air) (PS(A)) project aims to improve the NZDF's ability to collect high fidelity ISR data, for longer durations, against a range of targets," it said.

It is holding three workshops in January to hear back from industry, timed to get American, European and Australian involvement too.

"The workshops are designed to be brainstorming sessions that will identify innovative and viable opportunities."

Initially, any solution might be owned and operated commercially but in future phases Defence could take over ownership, it said.