By inviting Kim to meet him in China before a summit with Trump, Xi may be sending a message to Washington that "Beijing still has leverage over Pyongyang", according to Lim.
"In a word, Chairman Kim Jong Un's visit to China is an indication that the second North Korea-U.S. summit is drawing near", Moon said.
Moon said resolving the issue of the North Korea sanctions hinges on how fast North Korea denuclearizes and whether it receives reciprocal measures from the United States. But others say Moon simply made a symbolic, conciliatory gesture toward North Korea.
Tuesday was Kim's birthday.
In his annual New Year's speech last week, Kim renewed his commitment to denuclearisation of the Korean Peninsula but warned the United States of taking a "new path" if it doesn't ease sanctions. "China and the DPRK are friendly and close neighbours and it is also an important tradition for us to maintain friendly exchanges", Lu said, referring to North Korea's formal name.
Kim spent around half an hour touring a pharmaceutical factory operated by Tong Ren Tang, the largest producer of traditional Chinese medicinal products.
Chinese Foreign Ministry spokesman Lu Kang told a regular news briefing Tuesday in Beijing that Kim's visit had no bearing on USA trade talks.
In a related development on Thursday, South Korean Prime Minister Lee Nak-yon said at a government meeting that there are views in his country that Japanese leaders have been fanning anti-South Korea sentiment among Japanese people for political purposes, according to the Prime Minister's Secretariat.
Mr Moon said North Korea should take more concrete steps, such as abandoning its intercontinental and intermediate-range ballistic missiles and dismantling weapons production lines and other nuclear complexes, to secure United States concessions such as sanctions relief.
Pyongyang has a long history of playing major powers off against each other, with Kim's predecessor and grandfather Kim Il Sung adept at winning backing from the then Communist rivals Beijing and Moscow in turn.
By hosting North Korean leader Kim Jong Un for a fourth time, China has signalled again that it will not be sidelined in the diplomatic dance between its Cold War-era ally and Washington.
North Korean leader Kim Jong-un's recent trip to China reflected Kim's desire to continue talks with Washington and keep his denuclearization promise.
Conditions for resuming two key economic projects between North and South Korea - the Kaesong Industrial Complex, where Southern companies used to employ North Korean workers, and Southern tourism to Mount Kumgang in the North "have essentially been met already", he said. Experts agree that while neither the U.S. nor China is "winning" in the trade war, China may be at a disadvantage.
Recently, China may be doing more of the latter, says James Kim, pointing to ongoing rumours of "de facto loosening of sanctions implementation in China".
Kim's China visit also is leading to anticipation that the stalled North-U.S. denuclearization negotiations may gain traction.
Mr Moon, who has over the past year played mediator between North Korea and the USA, said at a news conference on Thursday that Seoul would cooperate with the U.S. in resolving the issue of sanctions on North Korea.