China must be and will be reunified with Taiwan, President Xi Jinping said on Wednesday (Jan 2) as he called for the two rivals to work together to realise the "historic task" of complete reunification.

"It is a historical conclusion drawn over 70 years of development of cross-strait relations, and a must for the great rejuvenation of the Chinese nation in the new era," Mr Xi said in a major speech at Beijing's Great Hall of the People to commemorate the 40th anniversary of "Message to Compatriots in Taiwan".

The message was a policy document issued by the National People's Congress - China's Parliament - on Jan 1, 1979, the same day China and the United States formally established relations after Washington broke ties with Taiwan.

It proposed ending military confrontation through dialogue and welcomed exchanges between the two sides, which have been separately governed since Chiang Kai-shek fled with defeated Kuomintang (KMT) or Nationalist forces to Taiwan in 1949 after losing a civil war to the communists.

Up until 1979, China had carried out routine artillery bombardment of Taiwan-controlled offshore islands, like Kinmen, close to the mainland.

But no peace treaty or formal end to hostilities has been signed since the detente, even as business, cultural and personal links have flourished.

Mr Xi sounded a largely conciliatory note in his speech on Wednesday. He called for wide-ranging "democratic consultations" between political parties and other representatives from both sides on cross-strait relations and future, and on establishing an institutionalised mechanism to promote cross-strait ties and peaceful development.

He also pledged to further institutionalise cross-strait economic cooperation and to forge a common market, reported Xinhua news agency. Both sides should enhance the free flow of trade, connectivity in infrastructure, exchange of energy and resources, and shared industrial standards, Mr Xi was quoted as saying.

Unification would be done under a "one country, two systems" approach that would "safeguard the interests and well-being of Taiwanese compatriots", and Taiwan will be guaranteed lasting peace, Mr Xi said.

Nonetheless, he repeated Beijing's long-held stance that it would not tolerate advocates of Taiwan's independence, who include supporters of Taiwan President Tsai Ing-wen.

"It's a legal fact that both sides of the Strait belong to one China, and cannot be changed by anyone or any force," Mr Xi said.

Tsai says no, thanks

Ms Tsai, who has refused to affirm the "one China" consensus reached between Taiwan and China in 1992, said in response to Mr Xi's address that democratically-governed Taiwan will never accept "one country, two systems".

"We have never accepted the '1992 Consensus', because it is defined by Beijing as 'one China', 'one country, two systems. (Mr Xi's speech) today only confirms our suspicions," Ms Tsai said at a press conference.

She was referring to a tacit understanding reached between the then KMT government and Beijing in 1992 that both sides of the Taiwan Strait acknowledge there is "one China", with each side having its own interpretation of what "China" means. China holds up the 1992 Consensus as the basis for cross-strait engagement.

Ms Tsai told reporters: "Most Taiwanese are resolutely opposed to 'one country, two systems. This is the 'Taiwan Consensus'."

She reiterated her position that dialogue between the two sides could proceed only if Beijing recognised the government in Taiwan as an equal.

Ms Tsai had, in her New Year's Day address, warned against continued threats from China. Her comments signalled that she was not backing down despite her party's recent municipal election loss to Taiwan's more Beijing-friendly KMT opposition, and the prospect of a tough campaign for next year's presidential election.

Mr Xi, meanwhile, is under pressure from growing criticism within the party over his handling of foreign affairs - notably strained relations with Washington, whose moves to support Taiwan have drawn China's ire.

Mr Xi reiterated in his speech that China will not give up the use of military force to ensure Taiwan returns to the fold. Beijing "reserves the option of taking all necessary measures against outside forces that interfere with peaceful reunification and against Taiwan independence separatist activities", he said.

Xi's approach

In power since 2012, when he was named General Secretary of the Chinese Communist Party, Mr Xi has made the "Taiwan issue" one of his priorities.

In November 2015, he held a landmark meeting with then Taiwan President Ma Ying-jeou of the KMT in Singapore, the first between Chinese and Taiwanese leaders since 1949.

Taiwan's semi-official Central News Agency said Mr Xi's speech has replaced former Chinese president Jiang Zemin's 1995 speech on cross-strait reunification as Beijing's guiding principle on further engagement with Taiwan.

The speech laid out five principles for managing cross-strait relations and called for all parties to shape a "Taiwan plan" under the "one country, two systems" policy Beijing applies to Hong Kong and Macau.

The five principles are:

1. China and Taiwan to work together to revitalise the Chinese race and realise reunification

2. Explore a "one country, two systems" approach suitable for Taiwan in order to achieve eventual reunification

3. Insist on the "one China" principle to safeguard the future of peaceful reunification

4. Deepen harmonious cross-strait development to lay the foundation of peaceful reunification

5. Foster a common spirit among the people to increase support for peaceful reunification

Mr Xi's formulation is an attempt at concretising the reunification process, and can be seen as the CCP's guidelines on pushing the process forward, Professor Wang Hsin-hsien of National Chengchi University told Central News Agency.

The formulation does not allow for the existence of the Republic of China, which Taiwan has been calling itself since 1949 and is tolerated by Beijing under the 1992 "one China" consensus, said Prof Wang.