This picture from North Korea's official Korean Central News Agency (KCNA) taken on March 27, 2018 and released on March 28, 2018 shows China's President Xi Jinping (R) shaking hands with North Korean leader Kim Jong Un in Beijing.
North Korean leader Kim Jong Un was treated to a lavish welcome by Chinese President Xi Jinping during a secretive trip to Beijing as both sides seek to repair frayed ties ahead of landmark summits with Seoul and Washington.  / AFP PHOTO / KCNA VIA KNS / - / South Korea OUT / REPUBLIC OF KOREA OUT   ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO/KCNA VIA KNS" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
THIS PICTURE WAS MADE AVAILABLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP.  /         (Photo credit should read -/AFP/Getty Images)
-/AFP/AFP/Getty Images
This picture from North Korea's official Korean Central News Agency (KCNA) taken on March 27, 2018 and released on March 28, 2018 shows China's President Xi Jinping (R) shaking hands with North Korean leader Kim Jong Un in Beijing. North Korean leader Kim Jong Un was treated to a lavish welcome by Chinese President Xi Jinping during a secretive trip to Beijing as both sides seek to repair frayed ties ahead of landmark summits with Seoul and Washington. / AFP PHOTO / KCNA VIA KNS / - / South Korea OUT / REPUBLIC OF KOREA OUT ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO/KCNA VIA KNS" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS THIS PICTURE WAS MADE AVAILABLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP. / (Photo credit should read -/AFP/Getty Images)
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(CNN) —  

Xi Jinping and Kim Jong Un attended an elaborate celebration in Pyongyang Thursday celebrating 70 years of diplomatic relations between China and North Korea, underscoring their alliance amid challenges posed by the United States.

Fireworks burst into the sky over the May 1 stadium in the North Korean capital, while enormous signs proclaimed that the two countries were “true and reliable comrades.”

“Long live the unbreakable friendship and union between the Democratic People’s Republic of Korea (DPRK) and the Chinese people,” one banner said.

A large group callisthenics and art performance is held at the May Day Stadium in Pyongyang on June 20.
Xinhua News Agency/Getty Images
A large group callisthenics and art performance is held at the May Day Stadium in Pyongyang on June 20.

In one image, composed of hundreds of people holding up cards, rainbows linked the Forbidden City in Beijing and the Arch of Triumph in Pyongyang, while both leaders looked on with broad smiles.

The performance was described as a display of “undefeatable socialism” in North Korean state broadcaster KCNA. In the evening, state media said both leaders held a “warm” banquet where each toasted the other and expressed their hopes for a “beautiful future” for relations between the two countries.

Chinese and North Korean flags are displayed during a mass gymnastic performance at the May Day Stadium in Pyongyang, North Korea.
Shen Hong/AP
Chinese and North Korean flags are displayed during a mass gymnastic performance at the May Day Stadium in Pyongyang, North Korea.

President Xi returned to China Friday afternoon, according to state media. His visit was the first by a Chinese leader in 14 years.

His two day state visit to North Korea comes just one week before Xi is expected to fly to the G20 summit in Osaka, Japan, where he will meet for bilateral talks with US President Donald Trump.

Spectators wave Chinese and North Korean flags as North Korean leader Kim Jong Un, left, and visiting Chinese President Xi Jinping attend a mass gymnastic performance at the May Day Stadium in Pyongyang, North Korea.
Yan Yan/AP
Spectators wave Chinese and North Korean flags as North Korean leader Kim Jong Un, left, and visiting Chinese President Xi Jinping attend a mass gymnastic performance at the May Day Stadium in Pyongyang, North Korea.

It remains to be seen whether they can break the deadlock in trade negotiations between the two countries after talks broke down unexpectedly at the beginning of May.

In response, the Trump administration increased tariffs to 25% on an estimated $200 billion of Chinese imports.

A large group callisthenics and art performance in Pyongyang for Xi Jinping and Kim Jong Un on June 20.
Xinhua News Agency/Getty Images
A large group callisthenics and art performance in Pyongyang for Xi Jinping and Kim Jong Un on June 20.

North Korea’s diplomatic relationship with the US has been chilly as well since February when Trump walked out of nuclear disarmament talks in Hanoi, Vietnam, with Kim Jong Un.

No further negotiations around the surrender of Pyongyang’s nuclear arsenal are planned at this time.

Xi Jinping, second from left, and his wife Peng Liyuan, left, and Kim Jong Un, second from right, and his wife Ri Sol Ju, right, in Pyongyang, North Korea.
Huang Jingwen/AP
Xi Jinping, second from left, and his wife Peng Liyuan, left, and Kim Jong Un, second from right, and his wife Ri Sol Ju, right, in Pyongyang, North Korea.

But some analysts said that the two-day trip by Xi could indicate some movement on the stalled US talks, saying China is keen to showcase its potential contribution to improving relations between the two countries.

“If China’s mediation can prove helpful, it would also help demonstrate the usefulness of China to the United States as a constructive partner over key regional issues,” said Tong Zhao, a fellow at the Beijing-based Carnegie-Tsinghua Center for Global Policy.

China’s state broadcaster CCTV quoted Kim as saying 250,000 people welcomed the Chinese leader in the streets of the North Korean capital Thursday. Both Xi and Kim held bilateral talks on Thursday although only Chinese state media addressed the ongoing tensions with Washington.

According to China’s Xinhua, Xi told Kim that “the international community” was hoping for further successful talks between North Korea and the US on denuclearization on the Korean Peninsula.

Xi previously visited Pyongyang in 2008, when he was China’s vice president and when Kim Jong Un’s father, Kim Jong Il, ruled North Korea.

His trip Thursday was the first visit of a Chinese leader to North Korean since 2005, a time period marred by mutual mistrust and, at times, outright loathing between the two countries.

CCTV previously reported at the start of the trip that Xi said the relationship between China and North Korea is a “strategic choice made by both sides and won’t be shaken no matter how the international situation changes.”

CNN’s Serenitie Wang contributed to this article.