UPDATED 7.35pm Significant changes for the Defence Force are being foreshadowed in a White Paper released today.

The plans, costing around $20 billion over 15 years, will see changes made across all three branches of the armed forces.

Released at Parliament this morning, it earmarked funding equivalent to one per cent of New Zealand's GDP for defence - around half the amount spent by Australia and the United Kingdom.

The Prime Minister said some of it will be able to be funded out of the Defence Force's depreciation allowance, but over time future government Budgets will have to make bigger allowances for defence spending.

"And that reflects the fact that we want to keep defence at arguably no less than one percent of GDP in terms of spending and probably a bit more over time."

Key said the growth in military spending by South East Asian Nations and other factors makes defence more important and complex than ever.

"The emergence of ISIL, heightened tensions in the east and south China seas, and the rapid evolution and spread of cyber threats are just a few examples. New Zealand's geological no longer provides the protection it once did."

Defence Minister Gerry Brownlee said the plans will give the Defence Force funding certainty, to enable it to plan with confidence for 2030 and beyond.

Brownlee said the exact size of expansion is to be determined as they work through the next phase of enhancing capabilities.

"So I don't have a specific set of numbers. I can't say it's 10, I cant say it's 100 but it will be a significant number of people who are deployed into the armed forces, who will specialise to a greater extent this sort of deterrent."

LISTEN: Gerry Brownlee speaks to Larry Williams.

He describes the investment plans as responsible and timely.

Up for replacement are the Air Force’s 757 aircraft, its Hercules C-130s and the P3 Orions.

Key said Navy’s ANZAC frigates are also slated for replacement along with other defence upgrades.

"As well as investing in new capabilities such cyber security support and additional intelligence personnel to support military operations."

A new ice-strengthened offshore patrol vessel will be introduced, while naval tanker HMNZS Endeavour will also be replaced ... as will the dive ship HMNZS Manawanui.

Extra resourcing is to be put into intelligence and cyber support, and the Army’s battlefield systems will be digitised.

On top of this will be upgrades for special forces equipment, an upgrade of the Army’s light armoured vehicles, and continuing replacement of land combat weapons.

It said terrorism will continue to have an important influence on state decision-making, with respect to protection from, and response to, potential attacks.

The White Paper warns of instability in the Middle East, and the practice of ISIS and Al Qaeda to encourage their supporters to carry out attacks globally.