The timing is likely to raise eyebrows at the White House as it comes one week before the G20 summit in Japan, where US President Donald Trump expects to meet with Xi to discuss their trade war.

China and North Korea have worked to improve relations in the past year after they deteriorated as Beijing backed a series of UN sanctions against Pyongyang over its nuclear activities.

The North’s leader Kim Jong-un travelled to China -- his country’s sole major ally -- four times in the past year to meet Xi.

But Xi had yet to reciprocate until now. It will be the first trip there by a Chinese president since Hu Jintao went in 2005.

With Beijing and Washington at loggerheads over trade, China is keen to remind Trump of its influence in Pyongyang, with whom his nuclear negotiations -- a point of pride for the US president, who faces an election next year -- are also at a deadlock.

“The signal would be that China remains a critical stakeholder,” said Jingdong Yuan, a professor specialising in Asia-Pacific security and Chinese foreign policy at the University of Sydney.

“You cannot ignore China and China can play a very important role,” he told AFP. Xi could thus use the trip as a “bargaining chip” in the US-China trade war, he added.

According to an informed source in Pyongyang, Beijing was keen to arrange a visit to North Korea ahead of any encounter between Xi and Trump at the G20 summit -- with trip logistics finalized only last month.

In recent days, hundreds of soldiers and workers have been sprucing up the Friendship Tower in Pyongyang, pruning bushes and replanting flowerbeds on the approaches to the monument, which commemorates the millions of Chinese troops Mao Zedong sent to save the forces of Kim’s grandfather Kim Il-sung from defeat during the Korean War.

A detachment of soldiers in white jackets was also seen outside the Liberation War Museum -- which includes a section on the Chinese contribution -- potentially indicating that it may be on Xi’s itinerary.

‘Four to zero’

It will be Xi’s first trip to North Korea since taking power in 2012, though he visited the country as vice president in 2008.

“China and the DPRK are friendly neighbors,” CCTV said, adding that Xi and Kim have reached a “series of important consensus” in past meetings and that a new chapter of bilateral relations had begun.

In contrast, Kim Jong-un has gone to China multiple times over the past year -- an unbalanced exchange that has not gone unnoticed in Pyongyang.

According to diplomatic sources in the North Korean capital, after Kim’s many trips to meet Xi, there were increasingly strong feelings in Pyongyang that the Chinese leader should reciprocate for reasons of saving face.

“From a North Korean perspective, it’s time for Chairman Xi to visit,” said John Delury, an expert on US-China relations and Korean Peninsula affairs at Yonsei University in Seoul.

“They do keep score and it’s like four to zero,” he recently told AFP. “So far, Xi has approached China-North Korea relations very much as a function of US-China relations and kind of calculated in terms of that.”

The visit also comes as negotiations between Trump and Kim have soured after a second summit in February broke up without a deal, failing to agree on what Pyongyang would be willing to give up in exchange for sanctions relief.

Since then, Kim has accused Washington of acting in “bad faith” and given it until the end of the year to change its approach.

Still, the nuclear situation is “under control for now,” said Delury.

“That creates a space, a window where Xi could make a visit without expecting like a missile test the day he leaves or something like that,” he said. (AFP)