Xi Jinping on Friday encouraged China to mobilize against aggression by the U.S. and to be prepared for a second conflict against its old enemy from the Korean War.

On Friday, the general secretary of the Communist Party of China Central Committee and chairperson of the Central Military Commission, warned the U.S. not to underestimate China as it did during the Korean War.

Xi said China will never allow its sovereignty, security and development interests to be undermined. He also declared the Chinese people are not to be trifled with in a speech in Beijing during a ceremony marking the 70th anniversary of China's entry into the Korean War,

Xi asserted any act of unilateralism, monopolism and bullying - a clear reference to the Trump administration - will not work, and will only lead to a dead end.

"Let the world know that the people of China are now organized, and are not to be trifled with," Xi said in quoting Mao Zedong, founding father of the People's Republic of China.

Xi said China will expedite the modernization of its armed forces, the People's Liberation Army (PLA), which consists of five armed services.

"Without a strong army, there can be no strong motherland," he said.

Xi's renewed call to arms was similar to one he made Monday when he called on the Chinese people to "keep their faith in ultimate victory." He said the spirit among the Chinese forged during the Korean War wll inspire them to "prevail over all enemies" this time.

He described the spirit forged during the Korean War as a "very precious spiritual wealth." Xi spoke during a visit to the Korean War exhibition at Beijing's Military Museum of the Chinese People's Revolution.

He said this spirit will "inspire the Chinese people and the Chinese nation to overcome all difficulties and obstacles, and prevail over all enemies."

Chinese political pundits say Xi is trying to forge a wartime mentality that will prepare the Chinese for a war against the U.S.

Xi's speech had a "two-pronged message" for domestic and overseas audiences, noted Junfei Wu, deputy director of Hong Kong think tank the Tianda Institute.

"Internally, Xi took this opportunity to build a wartime mentality to forge unity among the party leadership before the Fifth Plenum, while rallying the morale of the Chinese people as China's economy is facing challenging years," said Wu.

Wu noted that at the beginning of the Korean War, the U.S. misjudged China's determination to intervene in the conflict.

"They thought China would not send troops into the Korean peninsula. But China did. Xi's speech and Beijing's high-profile commemorations are clear warning signals to the U.S. not to underestimate Beijing's determination to safeguard its core interests," he said.