"In the end the decision that we have made is based on what is in the best interest of our national security," Defense Minister Peter Dutton told a joint news conference in Washington.

France was outraged and accused its US ally of stabbing it in the back after Australia canceled a multibillion-dollar package for conventional submarines as it announced a new three-way alliance with the United States and Britain.

As the United States sought to do damage control, Dutton said it was important to "look at the facts."

Australia, which has growing concerns about China, had existing submarines that after a life extension would only have given the country an edge going into the 2040s, he said.

"Beyond that, the clear advice to us from chief of navy and the chief of the defense force has been that a conventional diesel submarine was not going to provide us with the capability into the 2030s -- the second half of the 2030s -- the 2040s and beyond and that we needed a nuclear-powered submarine," he said.

"And so we looked at what options were available to us. The French have a version which was not superior to that operated by the United States and the United Kingdom."