US Secretary of State Antony Blinken on Tuesday called on all United Nations member states to support Taiwan's "robust" participation in the U.N. system, contesting ongoing pressure from China to block the self-ruled island's access to international organizations.

Taiwan held the Chinese U.N. seat until Oct. 25, 1971, when it was voted out as representative of the country in favor of the People's Republic of China, which had won a civil war in 1949 and forced the republican government to flee to Taiwan.

China says Taiwan is one of its provinces and so it has the sole right to represent Taiwan internationally.

In a statement, Blinken said Taiwan's exclusion from U.N. forums "undermines the important work of the U.N. and its related bodies, all of which stand to benefit greatly from its contributions."

"The fact that Taiwan participated robustly in certain U.N. specialized agencies for the vast majority of the past 50 years is evidence of the value the international community places in Taiwan's contributions. Recently, however, Taiwan has not been permitted to contribute to U.N. efforts," Blinken said.

"That is why we encourage all U.N. member states to join us in supporting Taiwan's robust, meaningful participation throughout the U.N. system and in the international community," he said.

Blinken added that Taiwan was not present at global bodies, such as the World Health Assembly, despite its "world-class response" to the COVID-19 pandemic.

China, which has ramped up political and military pressure to force Taiwan to accept Chinese sovereignty, has said it is "gravely concerned" about U.S. advocacy for Taiwan in global organizations, and that efforts by Taiwan to expand its participation would fail.