Ahead of Moscow visit, Chinese President Xi Jinping said the Terminal High Altitude Area Defense (THAAD) installation jeopardises the strategic balance in the region.
China's President Xi Jinping said on Monday that the US deployment of an advanced anti-missile system in South Korea gravely harms the strategic security interests of China, Russia and other countries in the region.
Xi's comment came as he was preparing to visit to Moscow on Monday before travelling to Germany to attend the G20 summit.
China has repeatedly stated its opposition to the US Terminal High Altitude Area Defense (THAAD) anti-missile system and has called for its deployment to be stopped and the missiles that have already been installed to be removed.
China says the system's powerful radar can probe deep into its territory, undermining its security and a regional balance, while doing nothing to stop North Korea in its relentless pursuit of nuclear weapons and the missiles to deliver them.
"The US deployment of an advanced anti-missile system in South Korea gravely harms the strategic security interests of China, Russia and other countries in the region," Xi said in an interview with Russian media, according to China's state Xinhua news agency.
The US and South Korea say THAAD is solely aimed at defending the South from North Korea.
Relations between China and South Korea have been strained by THAAD deployment, though both sides have struck a more conciliatory tone since President Moon Jae-in took office in South Korea in May.
China and Russia have maintained close communication and coordination on the issue and held very similar views on it, Xi said.
"Beijing and Moscow are steadfastly opposed to the THAAD deployment and seriously suggest that relevant countries stop and cancel the installation," he said.
China and Russia would take "necessary measures," either together or independently, to protect their interests, Xi said, without elaborating.
Xi also said China and Russia should work together to boost trade and increase investment and financial cooperation, Xinhua reported.