Speaking as part of a joint security statement given alongside President Biden and Prime Minister Morrison, he said the three countries would be “working hand in glove to preserve security and stability in the Indo-Pacific”.
The pact will see the nations share technology and intelligence and allow Australia to deploy a fleet of nuclear powered submarines though Prime Minister Morrison was at pains to point out they would not be armed with nuclear weapons.
The leaders outlined the deal in a three-way virtual announcement from each of their capitals.
Johnson called it a momentous decision for Australia to acquire the technology.
“This will be one of the most complex and technically demanding projects in the world,” he said.
US officials said the partnership, which will also involve cooperation in areas including artificial intelligence, quantum technology and cyber, was “not aimed at any one country” but it will be widely seen as a reaction to the growing power of China in the region.
The pact, known as AUKUS, will involve Australia scrapping a multi-billion dollar program to build French-designed submarines and build its nuclear-powered fleet with U.S. and British technology instead.
Mr Johnson said the pact would last “for decades” and create “hundreds of highly skilled jobs” across the country.
He said: “Perhaps most significantly, the UK, Australia and the US will be joined even more closely together, reflecting the measure of trust between us, the depth of our friendship, and the enduring strength of our shared values of freedom and democracy.
“Now the UK will embark on this project alongside our allies, making the world safer and generating jobs across the United Kingdom.”
The newly-installed Foreign Secretary, Liz Truss, said the pact would “promote stability in a region that will become ever more important for the UK’s prosperity and security”.
In a statement published online, Downing Street said the new submarines “will promote stability in the Indo-Pacific and will be deployed in support of our shared values and interests”.
Mr Johnson said: “This partnership will become increasingly vital for defending our interests in the Indo-Pacific region and, by extension, protecting our people back at home.”