Japan relationship getting stronger: PM

Australia's relationship with Japan is getting stronger even if it won't be building our next fleet of submarines, Prime Minister Malcolm Turnbull insists.

Mr Turnbull has notified Japan and the other unsuccessful bidder - German company ThyssenKrupp Marine Systems - the estimated $50 billion project will go to French consortium DCNS.

When asked if the decision would upset the United States - which was supportive of the Japanese bid - he told reporters in Adelaide on Tuesday the choice was a sovereign decision for Australia.

Australian and Japanese leaders and their governments were thoroughly committed to the special strategic partnership between the two nations, "which gets stronger all the time".

"We are committed to our strong trilateral strategic engagement between Japan, Australia and the United States," Mr Turnbull said.