In a press conference on Wednesday, Chinese foreign ministry spokeswoman Hua Chunying said that China is “gravely concerned” about reports of four additional THAAD launchers landing in South Korea, and reiterated China’s stance on the issue.

Hua stressed that the deployment of THAAD damages China’s strategic security interests as well as the regional strategic balance. She added that the deployment undermines the cooperation of the US and China in working to denuclearize the Korean peninsula.

South Korea’s newly elected president Moon Jae-in was reportedly livid on Tuesday when he learned for the first time that four THAAD missile defense systems had arrived in the country, in addition to the two already deployed.