SINGAPORE — China will impose sanctions on U.S. officials who displayed “nasty” behavior over the issue of Taiwan, the Chinese foreign ministry said on Monday, according to CNBC’s translation.

The decision was revealed by the foreign ministry’s spokewoman, Hua Chunying, in response to a reporter’s question on what China would doin response to the U.S. lifting restrictions on its relations with Taiwan.

U.S. Secretary of State Mike Pompeo had earlier this month announced that his country will no longer limit contact between its officials and their Taiwanese counterparts. China slammed the decision and vowed to fight back.

China claims Taiwan — a democratic and self-ruled island — as its territory that must one day be reunited with the mainland,and insists that the island has no right to participate in international diplomacy of its own. The Chinese Communist Party has never governed Taiwan.

Experts have warned that Taiwan will remain a contentious issue in the bilateral ties between the U.S. and China. Former Australian Kevin Rudd, a long-time China watcher, told CNBC last week that Pompeo’s move could upend a major foundation underpinning U.S.-China relations.

Rudd was referring to the “one China policy,” the principle in which the U.S. and the international community recognize that there’s only one central Chinese government — under the Communist Party of China in Beijing.