Taiwan split from mainland China at the end of the Chinese civil war in 1949.
Beijing regards Taiwan as part of its territory, and says it will use force if it declares independence.
Beijing and Taipei both claim they are the legitimate government of all China.
Taiwan has been a multi-party democracy since 1996.
Taiwan's defence ministry says China now has nearly 1,000 missiles aimed at the island.
The US is Taiwan's major arms supplier and has warned China that any attack would be viewed with "grave concern".