North Korean leader Kim Jong Un left Beijing after talking and dining with Chinese President Xi Jinping, according to South Korean media, in a show of unity as they engage in delicate negotiations with President Donald Trump's administration.

Kim spent a little more than a day in the Chinese capital and was en route to Pyongyang by 2 p.m. Wednesday local time, Yonhap News Agency of South Korea reported, citing unidentified officials. His delegation was seen off by high-ranking Chinese officials and honor guard at a Beijing train station and could return to North Korea as soon as Thursday morning, Yonhap said.

The trip — Kim's fourth to China since March — suggests negotiations over North Korea's nuclear arsenal are gaining momentum after months without high-level diplomatic exchanges. Trump is seeking a second summit with Kim to reenergize talks that have made little headway since their first meeting in June, saying Sunday a date would be announced "in the not-too-distant future."

Given the limited speeds of the heavily fortified Kim uses to travel, it could takes 12 to 14 hours for him to reach the Chinese border city of Dandong, about 520 miles away, meaning he might spend the night in one of its luxury carriages before returning home.

Kim spoke with Xi for about an hour Tuesday night, discussing ways to strengthen their ties and lay out strategy for a potential summit between Kim and Trump on curbing Pyongyang's nuclear ambitions, Yonhap reported, citing unidentified people familiar with the talks. The DongA Ilbo newspaper said that Xi hosted Kim at a banquet, which was held on the date believed to be North Korean leader's 35th birthday.

Kim could be looking to leverage his relationship with Xi, who Trump has accused of relaxing pressure on North Korea, to push the U.S. to make concessions in nuclear talks. The North Korean leader said in his New Year's address that he might take a "new path" in negotiations if Trump didn't ease trade, travel and investment restrictions.

While Kim was in China, Xi's government was in talks with a visiting U.S. delegation over a trade war that has been extracting a financial cost on the world's two biggest economies. For Xi, whose country provides a lifeline to North Korea's anemic economy, the meeting with Kim reminds Trump that China's cooperation will make any nuclear deal more effective.

Still, China has denied any interest in using North Korea as a bargaining chip and doing so risked undermining a source of stability in its strained relations with the U.S.

Kim visited a factory of Chinese traditional pharmaceutical company the next morning and returned to the state guest house. He left there around noon, Yonhap reported.

There has been no mention of the meetings so far in Chinese or North Korean state media. Video footage shown on South Korean and Japanese media showed streets being cleared of traffic for a convoy of luxury vehicles, supposedly shuttling Kim through Beijing.

Naoko Aoki, a nuclear security fellow at the RAND Corp. in Washington, said that Kim's delegation included officials focused on diplomatic and security policy and some key economic players haven't been seen. "Judging from the delegation lineup, the mission appears to place emphasis on North Korea's continuing diplomatic outreach and nuclear and security issues," Aoki said.

Kim traveled to China -- his most important security and trade partner -- before meetings last year with Trump and South Korean President Moon Jae-in. Trump complained after a similar China trip in May that Xi might have emboldened Kim to take a harder line before their own eventual meeting in Singapore.

China and Russia, who both wield vetoes on the United Nations Security Council, have called for easing sanctions to reward Kim's move last year to halt weapons tests and dismantle some testing facilities. While there have been reports of easier inspections at the North Korean border, China has denied that it's relaxing pressure on the regime.

Chinese Foreign Ministry spokesman Lu Kang told a regular news briefing Tuesday in Beijing that Kim's visit had no bearing on U.S. trade talks. "China and the DPRK are friendly and close neighbors and it is also an important tradition for us to maintain friendly exchanges," Lu said, referring to North Korea's formal name.