Why is China so angry about Taiwan president meeting US Speaker McCarthy?

US House Speaker Kevin McCarthy will host a meeting in California on Wednesday with Taiwan's President Tsai Ing-wen, part of a sensitive US stopover that has drawn Chinese threats of retaliation.

Here are the key issues in Taiwan-US, China-US and Taiwan-China relations, why China is so angry about the meeting and what it might do to express its anger:

WHY IS CHINA SO ANGRY?

Taiwan is a deeply emotive issue for China's ruling Communist Party, and for Chinese President Xi Jinping.

The People's Republic of China has claimed Taiwan as its territory since the defeated Republic of China government fled to the island in 1949 after losing a civil war with Mao Zedong's communists.

China has repeatedly called on US officials not to engage with Taiwanese leaders, viewing it as support for Taiwan's desire to be viewed as separate from China.

China has never renounced the use of force to bring democratically governed Taiwan under its control, and in 2005 passed a law giving Beijing the legal basis for military action against Taiwan if it secedes or seems about to.

HOW WILL CHINA REACT TO THE MEETING?

China staged war games around Taiwan last August after then-House Speaker Nancy Pelosi visited Taipei, and has threatened unspecified retaliation if the McCarthy meeting goes ahead.

While Taiwanese and US officials have said in the run-up to the McCarthy-Tsai meeting they have not seen any unusual activity from China's military, Taiwan is also on alert for any further Chinese drills.

Taiwanese and US officials have also said that by staging the meeting outside of Taiwan it may help tone down China's reaction.

Over the past three years or so, China's air force has flown almost daily into the skies near Taiwan, in which Taiwan calls "grey zone" warfare designed to test and wear out its forces. While China's air force has never flown into Taiwan's territorial airspace, it fired missiles high over the island after Pelosi's visit.

WHAT IS THE RELATIONSHIP BETWEEN TAIWAN AND THE UNITED STATES?

In 1979, the United States severed official relations with the government in Taipei and instead recognised the government in Beijing. A Taiwan-US defence treaty was terminated at the same time.

Post-1979, the US relationship with Taiwan has been governed by the Taiwan Relations Act, which gives a legal basis to provide Taiwan with the means to defend itself, but does not mandate that the United States come to Taiwan's aid if attacked.

While the United States has long followed a policy of "strategic ambiguity" on whether it would intervene militarily to protect Taiwan in the event of a Chinese attack, US President Joe Biden has said he would be willing to use force to defend Taiwan.

The United States continues to be Taiwan's most important international source of weapons, and Taiwan's contested status is a constant source of friction between Beijing and Washington.

WHAT IS TAIWAN'S POSITION AND DIPLOMATIC STATUS?

Taiwan's government says that as the People's Republic of China has never ruled the island it has no right to claim sovereignty over it or speak for or represent it on the world stage, and that only Taiwan's people can decide their future.

Taiwan's official name continues to be the Republic of China, though these days the government often stylises it as the Republic of China (Taiwan). Only 13 countries now formally recognise Taiwan after Honduras ended ties last month.

Taiwan's government says that as the Republic of China is a sovereign country and it has a right to state-to-state ties.

WHAT ARE RELATIONS LIKE BETWEEN TAIPEI AND BEIJING?

In one word - bad.

China views Tsai as a separatist and has rebuffed repeated calls from her for talks. Tsai says she wants peace but that her government will defend Taiwan if it is attacked.

She says the Republic of China and People's Republic of China are "not subordinate" to each other. Beijing says Tsai must accept that both China and Taiwan are part of "one China".