Thousands of troops stood at attention in perfect formation under a blue autumn sky in Pyongyang's main Kim Il Sung Square, named after Kim Jong Un's grandfather and the founder of the nation, as Kim made his way to the podium.
Kim was accompanied by senior Chinese Communist Party official Liu Yunshan and flanked by senior North Korean party and military officials.
Troop carriers could be seen mobilizing soldiers for the parade, expected to be one of the largest held by North Korea, which has been slapped with U.N. and U.S. sanctions for its nuclear weapons and rocket programmes.
Impoverished North Korea and rich, democratic South Korea, backed by the United States, remain technically at war after their 1950-53 conflict ended in a truce, not a treaty.
In a letter delivered by Liu, the most senior Chinese official to visit Pyongyang since leader Kim came to power following his father's death in 2011, Xi said China attached vital importance to its relationship with North Korea, China's official Xinhua news agency said.
China is North Korea's chief ally and its main trading partner, although ties have been strained over the North's nuclear programme.
Xi said in the letter that China had "been striving to treat the bilateral relations from a strategic and long-term perspective". Liu reiterated China's position that it wanted an early resumption of the so-called six-party talks aimed at reining in North Korea's nuclear ambitions.
"The Chinese side is willing to seek closer communication and deepen cooperation, pushing for a long-term, healthy and stable development of the Sino-DPRK ties," Xi said in the letter cited by Xinhua, referring to North Korea by its official name, the Democratic People's Republic of Korea.
Kim, who is in his early thirties, told the visiting Chinese delegation on Friday that North Korea was also keen to bolster ties, the North's official KCNA news agency said on Saturday.
Liu Yunshan, a member of the Standing Committee of the Political Bureau of the Communist Party of China Central Committee, presents a signed letter from Chinese President and General Secretary of the CPC Central Committee Xi Jinping to North Korean leader Kim Jong Un Source: AAP
Liu is the fifth-ranked member on China's ruling Communist Party's elite Politburo Standing Committee.
On Wednesday, a high-level U.S. military official said Washington believed North Korea had the capability to launch a nuclear weapon against the U.S. mainland and stood ready to defend against any such attacks. [nL1N128052)
However, a planned launch of a satellite, which had been expected by officials in Seoul to be a centrepiece of Saturday's celebrations, seems less likely to take place soon. Analysts and South Korean officials say there have been no visible signs of launch preparations.
