Australia also acquiring them will add risks of conflicts in the Indo-Pacific region and pose threats to Chinese submarines in accidental collisions, said Wu Riqiang, an associate professor of international studies at Renmin University.

“The submarines to be acquired by Australia will of course add to the capabilities of its navy forces, which should be viewed not in isolation but as part of the military alliance of Australia and the US to counter China,” Wu said. “Australia acquiring SSNs will definitely increase the risk of conflicts along the first island chain, such as in the South China Sea.

“My worry is that more submarines for Australia and the US will increase the threat to Chinese submarines. There could be more intelligence reconnaissance activities, which could increase the possibilities of collisions in the region.”

The idea of the first island chain was conceived during the Cold War, referring to the first line of defence against the influence of the Soviet Union and its allies. It runs from the Japanese archipelago through Taiwan, the Philippines and on to Borneo, enclosing China’s coastal seas.

The US Navy’s Office of Naval Intelligence has projected that China’s submarine fleet will grow to 76 submarines by 2030. The US currently operates 68, all of them nuclear.

“It’s a bit like the incidents that the United States and Britain had with the Soviet Union during the Cold War,” Wu said. “With more nuclear submarines and the alliance system, the US and Australia may advance an offensive naval strategy in the future.”

The longer-term military balance in the Indo-Pacific will shift, and the cost of conflicts will rise for other countries, according to Michael Shoebridge, director of defence, strategy and national security at the Australian Strategic Policy Institute.

South China Sea: the dispute that could start a military conflict

The military balance would be affected “well before the first nuclear submarine is built in Australia”, Shoebridge said.

“Aukus adds to the credibility of military deterrence in the Indo-Pacific, in a way that no doubt matters in Beijing,” he said, citing the Aukus statement that said cooperation in areas including cyber, artificial intelligence, quantum and undersea technologies would be strengthened.

Australia had long refrained from choosing sides between China and the US, but its attitude towards Beijing has hardened. Tensions were inflamed last year when Australia called for an investigation into the origins of the coronavirus, and a flurry of Chinese sanctions against Australian exports followed.

Australian academics have warned of the military threats posed by the modernisation of China’s People’s Liberation Army (PLA) and its expansion of maritime power.

According to a study released in August by Thomas Shugart from the Lowy Institute, a future Indo-Pacific dominated by China would present a grave possibility of military coercion by the PLA.

The prospect of Chinese military action against Australia remains remote, but China has the military and industrial potential to field a long-range power projection capacity that would dwarf anything Japan threatened Australia with during World War II, it said.

03:29

Nato says China presents ‘systemic challenges’

Nato says China presents ‘systemic challenges’

A military expert close to the PLA in Beijing said Australia was stepping to the front line by becoming part of the military means used by the US to contain China in the South China Sea.

“Having enhanced Australia’s military strength, the next step for the United States will be to vigorously play Australia’s role in the South China Sea,” said the expert, who requested anonymity.

The submarines, which will be acquired by Australia but can be used by the US, will enhance the overall strength of the United States in the western Pacific, “marking the beginning of major changes in the Asia-Pacific region”, they said.