China's foreign minister says a planned US missile defence system to protect South Korea from North Korea could threaten Chinese security.
Wang Yi told Reuters news agency that the system went "far beyond the defence needs of the Korean peninsula".
The US and South Korea announced plans to deploy the system after the North fired a long-range rocket this month.
China and Russia have previously said the system's radar could penetrate deep into their countries.
Talks over deploying the Terminal High Altitude Area Defence System (Thaad) come amid rising tension between the two Koreas over Pyongyang's recent rocket and nuclear tests.