The US defence secretary says China's pursuit of hypersonic weapons "increases tensions in the region" and has vowed the United States will maintain its capability to deter potential threats.
Lloyd Austin made the remarks in Seoul on Thursday following annual security talks with his South Korean counterpart that focused on challenges from China and North Korea and other issues facing the allies.
"We have concerns about the military capabilities that the PRC (People's Republic of China) continues to pursue," Austin said, referring to China's latest hypersonic weapons test in July.
"Again, the pursuit of those capabilities increases tensions in the region. It just underscores why we consider the PRC to be our pacing challenge," Austin said.
"We'll continue to maintain the capabilities to defend and deter against a range of potential threats from the PRC to ourselves and to our allies."
China's growing military muscle and its drive to end American predominance in Asia has triggered unease in Washington.
China's efforts to accelerate its military capabilities were highlighted by its July test of a hypersonic weapon capable of partially orbiting the earth before re-entering the atmosphere and gliding on a manoeuvrable path to its target.
Experts say the weapons system is clearly designed with a purpose of evading US missile defences, although China insisted it was testing a reusable space vehicle, not a missile.
On North Korea, Austin said he and South Korean Defence Minister Suh Wook discussed a wide range of topics including bilateral unity in the face of the threat from the North.
The two agreed that North Korea's advancement of its missile and other weapons programs "is increasingly destabilising for regional security", Austin said.
The US and South Korea remain committed to a diplomatic approach to North Korea, he added.
Despite severe pandemic-related economic hardships, North Korea has continuously rebuffed US offers to resume talks, saying Washington must first abandon its hostility toward the North.
The Biden administration maintains that international sanctions on North Korea will stay in place unless the country takes concrete steps toward denuclearisation.
Australian Associated Press