TAIPEI (Taiwan News) — Premier Cho Jung-tai (卓榮泰) on Tuesday rejected Chinese leader Xi Jinping’s comments on Taiwan.

During a call with US President Donald Trump, Xi said that “Taiwan’s return to China is an integral part of the (post-WWII) international order,” according to China’s foreign ministry.

Cho reiterated that Taiwan is “a fully sovereign and independent nation” and that “returning” to China is not an option for the 23 million Taiwanese, per CNA. He said Taiwan is crucial to regional security as well as global technological and economic development. Maintaining the status quo is therefore a matter of international concern, he said.

He emphasized that China cannot disrupt the status quo, saying Taiwan must strengthen its defense capabilities and stand together with countries that uphold democratic values.

On Sunday, Taiwan’s Ministry of Foreign Affairs condemned a letter written by China’s permanent UN representative Fu Cong to UN Secretary-General Antonio Guterres asserting sovereignty over Taiwan.

The letter criticized Japanese Prime Minister Takaichi Sanae for saying that a Chinese invasion of Taiwan could prompt a military response from Tokyo, according to China’s State Council. Fu called Takaichi’s comments “provocative” and “gravely erroneous and extremely dangerous.”

“Taiwan is China’s sacred territory, and how to resolve the Taiwan question is a matter for the Chinese people and brooks no foreign interference,” Fu wrote.

MOFA said the letter was “overbearing and unreasonable” and distorted historical facts. It also said the letter violated Article 2, Paragraph 4 of the UN Charter, which prohibits the threat or use of force in international relations.

The ministry said that after the end of World War II, the San Francisco Peace Treaty superseded the Cairo Declaration and the Potsdam Proclamation. The treaty did not transfer Taiwan to China, and China has never governed Taiwan, it added.