Speaking at the National People's Congress, the Chinese parliament, Xi did not identify enemies.
On the domestic front, Mr Xi in his speech also reiterated that the CCP is the leader of "everything" in China.
Both India and China are ancient civilizations with global influence, Modi said, adding that India will work with China to enhance high-level exchanges, deepen bilateral ties, strengthen coordination and cooperation in worldwide affairs to further a closer developmental partnership between the two countries and promote global and regional peace and development. "These separatist actions will be met with the condemnation of the people and punishment of the history".
"All acts and tricks to separate the country are doomed to fail and will be condemned by the people and punished by history", Xi told almost 3,000 delegates assembled at the Great Hall of the People facing Tiananmen Square.
"The Chinese people and the Chinese nation have a shared conviction that not a single inch of our land will be and can be ceded from China", Xi said, addressing the closing session of the NPC, the first by a President in recent years.
The session had earlier approved a range of new appointments, including that of key Xi ally Wang Qishan as vice president. "China also pursues peaceful development and in the same vein China will not occupy an inch of land of others", he said.
"The Communist Party is the supreme political leadership of the country and the fundamental guarantee to achieve the great rejuvenation of the Chinese nation", Xi said. The Communist Party of China's Central Committee had last month proposed to remove the limit on the terms of the President and Vice-President that prevented them from serving "no more than two consecutive terms".
"All acts and tricks to split the motherland are doomed to failure and will be condemned by the people", Xi told the National People's Congress.
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China fears secession by Taiwan and Hong Kong.
The call comes ahead of the Shanghai Cooperation Summit to be held in June in China where Modi and Xi are likely to meet on the sidelines.
He also sought to allay the concerns of the world over the rise of China, saying that China's development does not pose a threat to any other country.
Xi pledged to expand the Belt and Road, his signature foreign policy initiative of building ports, bridges and railways connecting Europe with Asia - but in an apparent response to the project's critics, said China wasn't seeking hegemony. CCTV now has more than 70 bureaux overseas, while China Radio International broadcasts in more than 60 languages.
"Only those who are accustomed to threatening others will see everyone as a threat", he added in an address that drew waves of applause from the legislators.
"Today, the creativity of the Chinese people is being unleashed to an extent like never before, which has been enabling our country to develop rapidly and stride forward at the forefront of the world", he said.
China was angered by legislation introduced by Donald Trump which encourages exchange visits by high-ranking United States and Taiwanese officials, thereby raising the island's diplomatic status.