China rebukes South Korean president for inappropriate comments on Taiwan.

Amid a simmering diplomatic dispute between China and South Korea, Beijing took its displeasure to Seoul on Sunday over President Yoon Sok-yul’s “wrong” remarks on Taiwan.

China’s outright refusal reflects the escalating tensions between the two countries, underlining the fragility of their diplomatic relations.

Beijing and Seoul traded barbs during a Reuters interview with Yoon this month, in which he described tensions between China and Taiwan as a “global issue” similar to North Korea, and blamed the recent heightened tensions on “attempts to change the status quo by force.”

China claims self-ruled and democratic Taiwan as its territory and has vowed to one day bring the island under its control, with Beijing insisting its dealings with Taipei are strictly internal affairs.

China’s foreign ministry said Vice Foreign Minister Sun Weidong was ordered Thursday to make “formal representations” to the South Korean ambassador over Yoon’s remarks.

The ministry said Sun said Ambassador Yoon’s remarks were “totally unacceptable” and expressed “strong dissatisfaction.”

China’s statement comes ahead of Yun’s state visit to a key ally the United States, which Beijing has blamed for arming Taiwan and encouraging pro-independence politicians.

Sun said that the Taiwan issue “concerns the Chinese themselves and no force can be allowed to interfere,” urging Seoul to “adhere to the one-China principle and be careful in words and deeds regarding the Taiwan issue.”

Chinese Foreign Ministry spokesman Wang Wenbin had criticized Yun’s remarks in the past, describing them as a “universally known fact” that the Taiwan issue could not be compared to the tensions on the Korean peninsula.

That prompted South Korea’s foreign ministry on Thursday to reprimand China for its “serious diplomatic rhetoric”.

Tensions in the Taiwan Strait have risen in recent years, with China launching military exercises earlier this month following a visit to the United States by Taiwanese President Tsai Ing-wen.