China sees self-governing democratic Taiwan as part of its territory awaiting reunification and has used its clout to diminish the island's presence on the world stage since Beijing-sceptic President Tsai Ing-wen took power in May 2016.

Last year was the first time in eight years that Taiwan was not granted access to the World Health Assembly (WHA) -- WHO's main meeting.

This year's WHA is to be held in Geneva from May 21-26 and the online registration deadline lapsed on Monday without Taipei receiving an invite.

"We believe the WHO is a non-political organisation pursuing the highest health standards for humanity and should not solely serve Beijing's political will," the Mainland Affairs Council (MAC) -- Taiwan's agency that handles official dealings with China -- said in a statement.

Taiwan's foreign ministry said on Tuesday it "regretted" that it had not been invited to the WHA.

"Health is a basic human right, as well as a universal value regardless of differences in race, religion, political beliefs, economic or social situations," the ministry said in a statement.

It added that under the WHO charter, Taiwan should be allowed "equal participation" in all WHO events.

WHO has not yet responded to AFP's request for confirmation it will not invite Taipei to this year's WHA.

China's foreign ministry spokesman Geng Shuang said Monday that the island was only able to attend the WHA from 2009-2016 because the previous Taiwan government had a consensus with Beijing that there is only "one China".

While the former administration touted the agreement as enabling cross-strait relations to flourish without compromising Taiwan's sovereignty, Beijing saw it as meaning that Taiwan and the mainland are part of a single China.

President Tsai and her independence-leaning Democratic Progressive Party have refused to acknowledge the principle which Beijing sees as the bedrock for relations.

"This damaged the political foundation for Taiwan's participation," Geng told reporters.

China has also been attempting to exert pressure on international companies to list Taiwan as a Chinese province on their websites, rather than as a separate entity.

The White House said on Saturday that China's aviation authorities had sent letters to 36 foreign airlines including US firms demanding they refer to Taiwan, Hong Kong, and Macau as Chinese territories.

"This is Orwellian nonsense and part of a growing trend by the Chinese Communist Party to impose its political views on American citizens and private companies," it said.