“It is a true honour to be here to convey a message of strong support and friendship from President Trump to Taiwan,” Azar said in his meeting with Tsai at the island’s Presidential Office.

“President Trump has signed legislation to strengthen the partnership between Taiwan and the United States, and in 2018, we opened a new American Institute in Taiwan – a brick-and-mortar commitment to our treasured friendship,” he said, referring to the US opening of a new headquarters compound for the American Institute in Taiwan (AIT), the US de facto embassy in Taiwan in the absence of formal relations.

Azar, who is the highest-ranking Cabinet member to visit Taiwan since the US switched diplomatic recognition to Beijing from Taipei in 1979, said the purpose of his visit was to seek cooperation with Taiwan on health issues.

“The particular focus of both my discussion with President Tsai and of our trip is highlighting Taiwan’s success on health in combating Covid-19 and to cooperate with the US to prevent, detect and respond to the health threats,” he said.

Tsai expressed her appreciation for the US’ strong support for Taiwan and its commitment to help the island expand its global participation, a move Beijing has found provocative and called a violation of America’s “one-China” policy.

“I believe under cooperation and efforts between the two sides, there will be more breakthroughs, not only in combating the pandemic, but also in other areas and exchanges bilaterally,” she said.

“I want to use this opportunity to thank President Trump, Secretary of State Mike Pompeo and Health Secretary Azar as well as many other American friends for their persistent recognition of Taiwan’s contribution to the world over the fighting of the pandemic,” she said, adding she also wanted to thank the US for its strong support for Taiwan’s “global participation”.

Azar also met the island’s health minister, Chen Shih-chung, on Monday afternoon, where he stressed that Taiwan and the US had a history of close collaboration in the field of health care and his visit “represents an acknowledgement of the US and Taiwan’s deep friendship and partnership across security, economics, health care and democratic, open, transparent values”.

“In the middle of Covid 19, it is critical that we support and recognise those who share those values and transparency of health care,” Azar said.

He said the WHO’s removal of Taiwan’s observer status from the WHA four years ago “deprived the world and international public health community of the significant expertise of the world class public health infrastructure of Taiwan”.

Beijing considers Taiwan a wayward province that must be returned to the mainland fold, by force if necessary. It strongly opposed and warned the WHO against admitting Taiwan, a move drawing strong criticism from Trump, who announced the US’ withdrawal from the global body from next year.

Asked if the Trump administration would invite Taiwan to join a possible new global health body, Azar said: “After our departure from the WHO [next July], we will work with others in the world community to find the appropriate vehicle for continuing the support on a multilateral and bilateral basis, global public health on the order the US that has done in the past.

“We will of course talk to Taiwan and other entities as we go forward, and [in terms of a] future visit, we enjoy this one right now and we will think about others in the future,” he said, rejecting media speculation that he was on the island to talk about forming a new international health group.

On Monday, Azar and Chen witnessed the signing of a memorandum of understanding on health cooperation by AIT director Brent Christensen and Yang Jen-ni, chairwoman of the Taiwan Council for US Affairs. The MOU was signed at the Central Epidemic Command Centre in Taipei.

Under the MOU, the two sides will strengthen cooperation on global health security, investigation and control of infectious disease, research, prevention and treatment of chronic disease and the development of drugs and vaccines.

Beijing has expressed its anger at the visit and threatened unspecified countermeasures.

Chinese foreign ministry spokesman Zhao Lijian said on Monday Azar’s trip seriously violated the US’ one-China policy and demanded that the US “stop any forms of official contacts with Taiwan to avoid sending the wrong signals” to Taiwan independence forces which would seriously damage the peace and stability of the region.

Observers said Azar’s high-profile historic Taiwan visit represented a new milestone in US-Taiwan relations.

“Compared with previous US officials who came to Taiwan to visit, Azar’s trip is a lot more high profile, meaning Washington no longer takes China’s response into account,” said Wang Ting-yu, legislator of Taiwan’s ruling independence-leaning Democratic Progressive Party.

Azar and his delegation arrived in Taipei on Sunday for a four-day visit via a US Air Force C-40B which is designed to be an “office in the sky” for senior US military and government leaders. For the first time in decades, the arrival of Azar on the military plane which bears the American flag on its tail was allowed to be broadcast live.

“This set up a new model for the non-diplomatic relationship between Taiwan and the United States, and represents a new milestone in US-Taiwan ties, as well as our efforts to expand our global presence,” DPP legislator Tsai Shih-ying said.

But Yen Chen-sheng, a political-science professor at National Chengchi University, said the Trump administration was sending a health secretary rather than the secretary of state or defence to Taiwan, meaning Washington was still aware of the risk of crossing Beijing’s red line.

“Though he is the most senior cabinet member to travel to Taiwan so far, he is still a health official who is here to deal with Covid-19 and other health cooperation issues with Taiwan,” Yen said, adding such an arrangement was carefully calculated to avoid crossing Beijing’s red line, yet strong enough to irk the mainland at a time US-China relations were at their lowest point since 1979.

In contrast to the steadily worsening relationship between mainland China and the US, which has seen them clashing on issues from trade and technology to defence and human rights, ties between Taipei and Washington have improved significantly since Tsai Ing-wen was elected the island’s president in 2016.

Beijing has time and again warned Washington against any form of formal interactions with the island, with which it has suspended official exchanges since Tsai took office four years ago and refused to accept the one-China principle.

Azar is scheduled to meet Taiwanese Foreign Minister Joseph Wu, Vice-President William Lai and former vice-president Chen Chien-jen. Both Lai and Chen are public health experts.