Taiwan has criticised what it called the World Health Organisation's "indifference" to the health rights of Taiwan people and for capitulating to China after the island failed to get invited to a meeting of the WHO decision-making body.
Taiwan is excluded from most global organisations such as the WHO, the UN health agency, because of the objections of China, which considers the island one of its provinces and not a separate country.
Taiwan had been lobbying for access to the forum, which opened on Monday, as an observer.
But no invitation came, the government said.
In a joint statement from Foreign Minister Joseph Wu and Health Minister Chen Shih-chung, the government said it would continue to seek participation.
"As a professional international health body, the World Health Organisation should serve the health and welfare of all humanity and not capitulate to the political interests of a certain member," Chen said, referring to China.
Wu expressed regret at the "WHO Secretariat's continued indifference to the health rights of Taiwan's 23.5 million people".
China says Taiwan can only take part if it accepts it is part of "one China," which Taipei's government will not do, and that only Beijing has a right to speak for Taiwan on the international stage and Taiwan has in any case been given the access it needs during the COVID-19 pandemic.
The formal decision not to include Taiwan on the agenda of the WHO's annual ministerial meeting, taken by WHO's general committee, was announced later on Monday by Bhutan's Health Minister Dasho Dechen Wangmo, who serves as president of the week-long talks.
During the brief WHO debate, Nauru and Eswatini spoke in favour of Taiwan's participation while China and its ally Pakistan voiced opposition, citing the "One China" principle.
"We urge relevant countries to stop politicising health issues and using Taiwan issues to interfere in China's internal affairs," Chen Xu, China's ambassador to the UN in Geneva, said.
Taiwan's statement said China was falsely claiming that appropriate arrangements have been made for Taiwan's WHO participation, adding that only the island's democratically elected government can speak for its people.
The WHO said in an emailed statement that its secretariat works extensively with Taiwan health experts and officials at a technical and scientific level.
Taiwan's observership was a question for its 194 member states to decide, it said.
US health secretary Xavier Becerra is due to address the forum on Tuesday.