The partnership plan, called Aukus, will provide Australia with nuclear-powered submarines to counter Chinese activities in the Pacific Ocean.
But China's foreign ministry spokesperson, Wang Wenbin, says the three nations have ignored the international community's concerns.
The UK's Chancellor of the Exchequer, Rishi Sunak, met with US President Joe Biden
and Australian Prime Minister Anthony Albanese in San Diego to announce the next stage of the Aukus partnership plan.
The pact doesn't increase the risk of nuclear proliferation, with the vessels carrying conventional weapons and the nuclear reactors being sealed shut.
“For the first time ever, three fleets of submarines will work together across both the Atlantic and Pacific oceans, ensuring our oceans free, open, and prosperous for decades to come”, said British Prime Minister Boris Johnson
China's more aggressive stance is concerning to the UK, which recently published its integrated review of foreign and security policy.
President Biden believes the US has no better partners than the UK and Australia when it comes to ensuring the security of the Pacific.
He expects to speak to Chinese leader Xi Jinping soon but did not say when.
China and the US are maintaining necessary communications, but Mr. Wenbin says the value and significance of communication is to enhance understanding, not just for the sake of communication.
Meanwhile, the US seeks to re-establish regular communications with China after communicating with them for 18 months about Aukus and seeking more information from them about their intentions.
Stay tuned for more updates on this developing story.