President Xi thundered against past efforts in Taiwan to become legally independent of China and said the two sides should pursue a "one country-two systems" model of unification that his government applied to Hong Kong in 1997.
The "Message of Compatriots in Taiwan" on January 1, 1979, declared an end to routine artillery bombardment of Taiwan-controlled islands close to China, marking a turning point from decades of hostility between the two sides.
While Xi said China would make "no promise to renounce the use of force", he often reiterated the notion that it is "willing to create broad space for peaceful reunification", indicating that Beijing may take a long-term approach as Tsai faces a tough re-election battle.
President Tsai Ing-wen (蔡英文) yesterday said that Taiwan and its people would never accept a "one country, two systems" arrangement and urged China to bravely embark on the path to democracy to fully understand the minds of Taiwanese.
She stressed that Taiwan has been fulfilling its responsibility in maintaining regional stability for the past two years but has in return received threats from Beijing. His father, Chiang Kai-shek, fled with defeated Nationalist forces to Taiwan in December 1949 after losing a civil war to the Communists.
This week's speeches could deepen the China-Taiwan gap if Xi pushes ahead or Taiwanese opposition party figures engage him against Tsai's will, scholars say.
No one or no party can stop the trend toward unification, the Chinese leader said in a speech devoted to Taiwan, calling independence for the self-governing island against history and a dead-end.
On Wednesday, he suggested that "political parties and people from all walks of life on both sides of the strait elect representatives" to engage in talks on the future of their relationship, saying an agreement that both sides belong to "one China" must be upheld in negotiations.
Xi's speech commemorated the 40th anniversary of a message sent to Taiwan in 1979, in which China called for unification and an end to military confrontation.
"Deviating from the one China principle will result in tension and turbulence in cross-strait relations, harming the interests of the Taiwanese compatriots", Xi said.
"With the current situation between China and Taiwan, I don't think there is that foundation of trust for any kind of in-depth discussion of debate on these issues", said Raymond Wu, managing director of Taipei-based political risk consultancy e-telligence, referring to Tsai's ideas.
When Jiang Zemin took power in Beijing, he largely continued Deng's policies - wooing the island by opening the doors to Taiwan entrepreneurs wanting to set up factories and businesses on the mainland and take advantage of its cheap labour and vast market.
"China must and will be united", said Xi in reference to unification with Taiwan, AFP reports.
This October also marks the 70th anniversary of the Communist Party's takeover of China, an occasion that Xi has been using to solidify his stewardship after repealing presidential term limits past year.
Beijing has won over more and more of Taipei's few global allies to cut diplomatic ties with the island and establish relations with China instead.
Experts are of the view that China is also aware of the fact that Taiwan's younger generation is drifting away from its influence and that they needed to address the issue.