A special security pack has been agreed between the UK, the U.S and Australia to share advanced technologies including nuclear-powered submarine know-how.
The pack will include , industrial bases and supply chains will also be shared.
Mr Johnson said the three nations were natural allies and that the alliance would “bring us closer than ever”.
“This partnership will become increasingly vital for defending our interests, and… protecting our people back at home,” he said.
The countries deem the agreement necessary to defending their interests in the Indo-Pacific region, where China has a growing military presence.
The pact could also see Australia dash a deal to build French-designed submarines, Australian media report.
On Wednesday, US President Joe Biden, UK Prime Minister Boris Johnson and his Australian counterpart Scott Morrison issued a joint statement on the launch of the new security partnership, labelled Aukus.
“As the first initiative under Aukus… we commit to a shared ambition to support Australia in acquiring nuclear-powered submarines for the Royal Australian Navy,” the statement said.
“This capability will promote stability in the Indo-Pacific and will be deployed in support of our shared values and interests,” it said.
The leaders said the aim was to “bring an Australian capability into service at the earliest achievable date”, adding: “Australia remains committed to fulfilling all of its obligations as a non-nuclear weapons state.”
It added that the defence pact would also focus on cyber capabilities, artificial intelligence and “additional undersea capabilities”