Kim Jong Un declared Saturday that North Korea was ready to fight "any kind of war" waged by the United States, as he presided over a huge military parade in the center of Pyongyang to mark the 70th anniversary of the ruling Workers' Party.

The highly orchestrated event included goose-stepping soldiers, convoys of rocket launchers and missiles, and fighter jets roaring overhead. It was the biggest such parade North Korea has ever held, part of Kim's efforts to bolster his leadership of the world's most closed and authoritarian state.

"We have stood up against the American imperialists, and we are ready for any kind of war against the United States," Kim said in a long speech before the parade, his first public address in three years.

"Our military's invincible spirit causes anxiety and fear to our enemies," said Kim, who in addition to leading the country as the "Great Successor" holds the post of first secretary of the Korean Workers' Party. "We can firmly declare that we can fight and win against the U.S. anywhere."

Wearing his trademark navy blue Mao suit and reading from notes as he stood on a balcony overlooking rows of soldiers in Kim Il Sung Square,Kim was flanked by generals decked out with medals.

But also at his side was Liu Yunshan, the fifth-most-senior official in China's Communist Party. The North's official Korean Central Television showed footage of the two men laughing and waving throughout the event. Analysts said it was significant that Liu featured so prominently at the event and wondered whether it signaled an improvement in the frosty relations between Pyongyang and Beijing.

After Kim spoke, rows of tanks, trucks bearing Scud missiles, and 107mm and 300mm rocket launchers rolled through the square, the center of the capital and home to the Korean Workers' Party headquarters.

A formation of military planes flying over the proceedings formed the symbol of the Workers' Party - a hammer, sickle and writing brush - and the number 70, to Kim's evident delight. Banners floating above the square read: "Long live the invincible Korean Workers' Party" while people held up cards saying: "Military-first policy" and "Protect the mother nation."

Analysts say that this year's parade, celebrating seven decades since the creation of the Korean Workers' Party, is about boosting the regime's claims to legitimacy and further enabling the 30-something leader to present himself as the rightful heir to the system established by his grandfather, North Korea's "eternal president" Kim Il Sung.

The surprising component of the weekend's events was the prominence of Liu, who greeted Kim with three hugs and a broad smile when he presented the North Korean leader with a letter from Chinese President Xi Jinping on Friday evening.

Relations between the neighbors, once called "as close as lips and teeth," have soured in the three years since Xi took office and made it clear that he thought little of Kim and his penchant for nuclear and missile tests. Kim did not attend China's own military parade, marking the end of World War II, in Beijing last month.

But Liu brought a letter from Xi that said China had "been striving to treat the bilateral relations from a strategic and long-term perspective in a bid to maintain, consolidate and expand the bilateral relations," according to China's official Xinhua News Agency, which carried reports of the letter prominently.

"Under the new circumstance, the Chinese side is willing to seek closer communication and deepen cooperation, pushing for a long-term, healthy and stable development of the Sino-[North Korean] ties," the letter said.

"The overt embrace of China and the overt diplomatic message was striking," said Adam Cathcart, an expert on China and North Korea who teaches at Leeds University in England. "This seemed like quite a concession on the part of the North Koreans after several years of giving them the cold shoulder."

Coming after last month's parade in Beijing, which was attended by South Korean President Park Geun-hye, Liu's prominence at Saturday's event showed that China was not playing favorites between the Koreas and wanted to be seen as the diplomatic power in Asia, Cathcart said.

"I don't have high expectations that North Korea is going to do what China wants, but we should be happy that somebody is talking to North Korea," he said.

The high-profile Chinese delegation - which also included a senior member of China's People's Liberation Army - appeared to have paid initial dividends.

North Korea had warned that it was preparing to test what it calls a rocket for launching satellites into space but which is widely seen as cover for a long-range missile program.

Analysts had speculated that the regime would conduct the launch in the days leading up to the anniversary, but that did not happen, causing some to wonder whether Beijing had leaned on Pyongyang to behave itself while Liu was in town.

Furthermore, satellite imagery suggested a launch was not imminent. "The absence of any visible preparations for a launch indicate it is increasingly unlikely that a test will be conducted this month," analysts Jack Liu and Joseph S. Bermudez Jr. wrote in a post for 38 North, a Web site dedicated to North Korea.