China 'has drawn up secret plans to invade Taiwan by 2020'

China is planning to invade the democratic island nation of Taiwan in 2020, according to a new book by an American analyst.

Ian Easton, a China affairs analyst, claims to have been privy to internal military documents, including a secret plan draw up by the People's Liberation Army (PLA) to attack Taiwan. 

This comes just days after Beijing warned the United States it must respect China's concerns on Taiwan to avoid causing disturbances in Sino-U.S. ties.

Mr Easton works for think-tank Project 2049 Institute, where he conducts research on defense and security issues in Asia, but lived in Taiwan for several years.

In his book, The Chinese Invasion Threat, he writes: 'China has made clear that its primary external objective is attaining the ability to apply overwhelming force against Taiwan during a conflict, and if necessary destroy American-led coalition forces,' according to right-wing website the Washington Free Beacon.

'Consequently, the PLA considers the invasion of Taiwan to be its most critical mission, and it is this envisioned future war that drives China's military buildup.'

The book also claims that Chinese President Xi Jinping told fellow Communist Party leaders in 2012 that China planned to invade Taiwan by 2020. 

In recent months the Chinese air force has conducted a series of drills around Taiwan, which have included bombers and advanced fighter jets, alarming Taipei. China has called the exercises routine and pledged to continue with them. 

China considers democratic Taiwan to be a wayward province and has never renounced the use of force to bring the island under its control. The United States has no formal ties with Taiwan but is bound by law to help it defend itself and is the island's main source of arms.

China regularly calls Taiwan the most sensitive and important issue between it and the United States, and has been upset by U.S. moves to expand military exchanges with Taiwan and continued U.S. arms sales to the island.

Chinese Foreign Minister Wang Yi made the stern warning during a meeting with visiting U.S. Secretary of State Rex Tillerson.

Wang explained China's position on the Taiwan issue to Tillerson and 'demanded the U.S. side earnestly respect China's concerns, appropriately handle the relevant issue and avoid bringing disturbances to China-U.S. relations', China's Foreign Ministry said. 

Beijing's relationship with Taiwan has been frosty since President Tsai Ing-wen won election on the island by a landslide last year.

China suspects that Tsai, who leads the pro-independence Democratic Progressive Party, wants to declare the island's formal independence, a red line for Beijing. Tsai says she wants to maintain peace with China.