BEIJING, March 30 (Reuters) - Nuclear submarine cooperation between Australia, the United States and Britain may may spark an arms race, the Chinese foreign ministry said on Thursday.

"Once 'pandora's box' is opened, the regional strategic balance will be disrupted, regional security will be seriously threatened," said Tan Kefei, a spokesperson at the Chinese defence ministry, during a regular press briefing.

The United States, Australia and Britain this month unveiled details of a plan to provide Australia with nuclear-powered attack submarines from the early 2030s to counter China's ambitions in the Indo-Pacific.

"China firmly opposes the establishment of the so-called 'trilateral security partnership' between the United States, the United Kingdom and Australia. This small circle dominated by Cold War mentality is useless and extremely harmful," Tan said.

Tan added such cooperation was an extension of the nuclear deterrence policy of individual countries, a game tool for building an "Asia-Pacific version of NATO" and seriously affected peace and stability in the Asia-Pacific region.