The defence minister has announced a $1.58 billion investment in maritime security, ahead of the Budget.

Chris Penk said the government would invest in drone systems, ship maintenance, and work to replace an ageing naval fleet.

The Budget, which would be delivered on Thursday, would provide $700 million to implement projects identified in the Defence Capability Plan, on top of an additional $880m of operating funding over the next four years - or $134.5m per annum.

Defence Minister Chris Penk announcing a $1.58 billion investment in maritime security in Auckland. Photo: NICK MONRO / RNZ

The Maritime Fleet Renewal programme will receive an unspecified amount for two types of drones, alongside $51m in operating funding. One would be used for long-duration intelligence, surveillance, and reconnaissance over the southwest Pacific. The other would be polar-capable, and used to conduct missions from Navy vessels in the Southern Ocean.

It would also contribute $215m toward critical maintenance on the vessels Te Kaha, Te Mana and Canterbury.

Penk said New Zealand's prosperity and security depend on the sea.

"For many years, New Zealand's geographic distance has been seen as a shield from instability elsewhere in the world."

"However, recent events have served as a reminder of how quickly disruptions to international shipping routes can affect economies and supply chains across the globe. The oceans are not a barrier to danger, but a vital national interest that must be actively secured."

Funding would also be used to deliver new and upgraded training facilities and continue the long-term Homes for Families programme.