The upcoming visit of a senior US official to Taiwan is evidence of the healthy relationship between the two sides and indicative of Washington's dwindling concern about upsetting Beijing, observers say.

US Health and Human Services Secretary Alex Azar is set to lead a delegation to the self-ruled island on Sunday, according to Taipei. The American Institute in Taiwan (AIT), the United States' de facto embassy in Taipei, also announced the visit but did not give a date.

Azar is the highest-ranking member of the US cabinet to visit Taiwan since Washington severed ties with the island in favour of establishing formal relations with mainland China in 1979. He is also the first senior US official to visit Taiwan since US President Donald Trump signed the Taiwan Travel Act into law in 2018.

Beijing has been critical of Azar's planned trip, describing it as a violation of the "one China" policy the US promised to observe on the establishment of diplomatic ties with Beijing.

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.

Against that backdrop, some Taiwanese politicians have suggested there may be the possibility of a normalisation of US-Taiwan relations.

"The fact that the AIT has officially announced the planned visit of Azar and identified him as the highest-ranking cabinet member to visit Taiwan shows the United States has begun normalising its relations with Taiwan and no longer takes Beijing's views into account," said Wang Ting-yu, a politician from the ruling Democratic Progressive Party who sits on the parliamentary foreign and defence affairs committee.

The recent enactment of several pieces of legislation that support Taiwan was further evidence of normalising ties, he said.

Since 2018, the US Congress has approved at least five pieces of legislation relating to Taiwan, including the Taiwan Travel Act, which encourages high-level government exchanges between the two sides, and the Taiwan International Participation Act, which calls for the US to advocate for Taiwan's membership or observer status in international organisations.

Last year saw the passage of the Taiwan Assurance Act - which mandates a presidential review of the state department's guidelines on US-Taiwan relations and directs the defence department to include Taiwan in military training exercises - and the Taiwan Allies International Protection and Enhancement Initiative Act, which directs the state department to tell Congress about government moves aimed at strengthening Taiwan's diplomatic relations "partners" in the Indo-Pacific.