Defence Minister Christopher Pyne has backed Japan's plans to massively increase its defence spending.

The Japanese Government is set to refit its Izumo helicopter carrier so that it can deploy the US-made F35 Joint Strike Fighter.

Critics say that an aircraft carrier would give Japan a strike capability that would violate its pacifist constitution, which limits the use of force to self-defence only.

The nation is also planning to buy cruise missiles that opponents say would violate its pacifist principles too.

Mr Pyne has inspected the Izumo during a trip to Tokyo for meetings with defence counterparts.

“The Australian Government supports Japan increasing its military capability both from a defence point of view and from a point of view of ensuring it has a forward deployment capacity,” Mr Pyne told the ABC.

“So the Izumo being capable of carrying F35's ... is something the Australian Government welcomes and we would like to see Japan taking on more responsibility in north Asia for the security and stability of the region.”

Japanese Prime Minister Shinzo Abe has made a number of moves to re-draft Japan’s constitution, which was written for its by the United States at the end of the second World War.

New defence guidelines approved late last year says Japan needs to increase its missile defence and fighter capability due to North Korea's missile and nuclear threats.

“Another meeting between President Trump and the President of North Korea is a welcome development as long as it leads to outcomes — and the outcome we want is the denuclearisation of the Korean Peninsula,” Mr Abe said.

“We haven't seen concrete steps from the DPRK yet in denuclearisation.”

Japan's defence guidelines also raise concern about China's military activities in the region.

Mr Pyne is in Japan to negotiate a defence cooperation agreement for Australian and Japanese defence forces cooperate more effectively.

An example of the current struggle came during the Fukushima earthquake and tsunami, when an Australian C17 aircraft flew in equipment but could not unload it because of a lack of administrative procedures.

Reports say the current discussions are focusing on the legal status of Australian troops in Japan.

Mr Pyne says the agreement could be signed in the first quarter of this year.