"Today we are closer than ever before to the goal of the great rejuvenation of the Chinese nation, and - more than any other time in history - we need to build a strong people's military". "We will never seek aggression or expansion, but we have the confidence to defeat all invasions", said the president as quoted by China's state news agency Xinhua.
China celebrated the 90th birthday of its People's Liberation Army on August 1 by officially introducing a naval logistics base in Djibouti, between the Red Sea and Gulf of Aden.
"We do not allow any individual, any organisation, any political party, at any time or by any means to split any single piece of Chinese territory", said Xi, who commands the world's largest standing army.
"No-one should expect us to swallow the bitter fruit of damage to our sovereignty, security and development interests".
Xi also reaffirmed comments he made on Sunday regarding the need for the PLA to transform into a modern fighting force by cutting troop numbers and boost its use of military technology.
China is locked in a number of territorial disputes - both on waters and land - with various countries.
China claims India's Arunachal Pradesh as its own and calls it South Tibet. China considers the self-governing democratic island Chinese territory.
Xi, who commands the PLA as chairman of the Central Military Commission, has frequently spoken of his "China Dream" to restore China to a leadership position in worldwide affairs with a modern, far-reaching military force to match. "Peace must be safeguarded", Xi, wearing a camouflage military suit, said in a speech at the expansive Zhurihe training base in the Inner Mongolia Autonomous region.
That followed similarly high-profile military reviews in Beijing in 2015 and Hong Kong in June.
"The world is not all at peace".
According to the state media, over 300 people attended the opening ceremony including the deputy commander of Chinese Navy Tian Zhong and Defence Minister of Djibouti.