China has stepped up military and diplomatic pressure on Taiwan since Tsai Ing-wen came to power in 2016, as her government refuses to accept that Taiwan is part of "one China."

A Taiwanese coffee chain has become the latest business to bow to pressure from Beijing after Chinese web users threatened a boycott over a visit to one of its stores by the island's president.

Tsai Ing-wen stopped off at a Los Angeles branch of the 85C Bakery Cafe this week during a US stopover in which she became the first Taiwanese leader to give a public speech on American soil in 15 years.

Taiwan is a self-ruled democracy that considers itself a sovereign state but has never declared formal independence.

China views the island as part of its own territory and is always swift to condemn any move that could be interpreted as de facto diplomatic recognition of the government in Taipei -- such as allowing Tsai to transit on formal diplomatic business.

Internet users on the mainland lashed out at the coffee chain over Tsai's visit, with comments flooding its official Weibo account, China's popular Twitter-like platform, many with boycott threats.

"Get out of mainland China!," read one angry message.

"85C is a 'Taiwan independence' two-faced company. We mainland Chinese should boycott this kind of garbage company," said another post.

Taiwan, China, and the US are the main markets for 85C, which also has branches in Australia and Hong Kong.

In a statement Wednesday, the company declared its "firm support for 'one China'" and referred to Tsai as "leader of the Taiwan authority" -- a term used by the Chinese government and media.

The company "opposes any behaviour and remarks that divide the feelings of the compatriots on the two sides and we will serve customers under the belief that the two sides are the same family," it said.

A growing number of international companies including airlines and hotels are bending to Beijing's will and listing Taiwan as part of China.

In May, US clothing retailer Gap apologised to Beijing over a T-shirt with a map showing the mainland but omitting Taiwan, prompting hundreds of people to complain on Gap's Weibo account.

Tsai's office condemned what it called "improper tactics that disrupt market order and the freedom of speech," over the coffee shop row.

China has stepped up military and diplomatic pressure on Taiwan since Tsai came to power in 2016, as her government refuses to accept that Taiwan is part of "one China."