Pyongyang, North Korea - China's President Xi Jinping hailed an "invincible friendship" with Pyongyang on arrival in North Korea Monday, his first trip abroad this year after hosting back-to-back summits in Beijing.

China, Washington's chief geopolitical rival, has been North Korea's main trading partner by far for decades and a key source of diplomatic and economic support for a country hit by multiple international sanctions.

Military officers lined a red carpet as an Air China plane carrying Xi arrived for his first visit since 2019, video from Xinhua showed.

Kim and his wife Ri Sol-ju welcomed Xi, who was accompanied by his wife Peng Liyuan.

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The two leaders shook hands, and children presented flowers to Xi and Peng, while a banner reading "We warmly welcome Comrade Xi Jinping" and hailing the two countries' "unbreakable friendship" hung below Chinese and North Korean flags.

Xi makes the trip after hosting US President Donald Trump and Russia's Vladimir Putin separately in Beijing and as North Korea's nuclear talks with Washington remain deadlocked.

The White House said last month that Xi and Trump "confirmed their shared goal to denuclearize North Korea" during their summit in Beijing.

However, leader Kim Jong Un's powerful sister said on the eve of Xi's arrival that North Korea's nuclear weapons program was "the line of no retreat."

South Korea's President Lee Jae Myung said Monday that Seoul should not give up on North Korea's denuclearization, adding that "North Korea is still producing nuclear material even at this very moment."

Minseon Ku, a diplomacy professor at DePaul University, told AFP that "Beijing probably has accepted North Korea as a nuclear state," but Xi "will probably tell Kim that China wants stability more than anything."

China has "always prioritized stability and is currently having to manage its relations and differences with the US," Ku said.

Seong-Hyon Lee, a visiting scholar at the Harvard University Asia Center, also said Beijing is shifting towards "underwriting regime durability" rather than seeking to coerce North Korea into denuclearization.

"China's broader regional strategy benefits from a stable, heavily armed, and aligned buffer state that absorbs US and allied military bandwidth," he told AFP.

North Korea has repeatedly declared itself an "irreversible" nuclear state since Kim and Trump's 2019 summit collapsed over the scope of denuclearization and sanctions relief.

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Kim has also been emboldened by the war in Ukraine, securing critical support from Moscow after sending troops to fight alongside Russian forces.

Some analysts say the summit could be Xi's way of countering Russia's growing influence over North Korea, but DePaul's Ku stressed that "overall, Moscow is not a major power like China."

"Moscow-Pyongyang power relations are more equal than Beijing-Pyongyang; Moscow needs Kim for their war in Ukraine as much as Kim needs technology sharing and food from Russia," she said.

In an article published on the front page of North Korea's Rodong Sinmun, Xi pledged closer cooperation.

"No matter how the times change or how the international situation evolves, the traditional friendship between China and North Korea is always invincible," Xi wrote.

Xi last met Kim in September, when he invited the North Korean leader and Putin to a military parade in Beijing marking the 80th anniversary of the end of World War II.

Jun Sang-gab (65), a South Korean tour guide who lives near the inter-Korean border, said he hopes "North Korea opens its economy" and follows China's development model.

"If they (the North) establish themselves economically, there won't be any incidents like armed unification or war" on the Korean peninsula, he told AFP.

Trump has made little progress on North Korea, especially on the nuclear front, despite his earlier high-profile summits with Kim.

North Korea is also the only country with an official, binding military alliance with China.

North Korea could also serve as a useful counterweight to US partners in the region, including South Korea and Japan, analysts said.

Long-frosty China-Japan ties have deteriorated since Prime Minister Sanae Takaichi, a security hawk, suggested last year that Tokyo might intervene militarily in any Chinese attempt to take over Taiwan.

"As China's international standing rises, Beijing is likely seeking to draw Pyongyang more actively into its diplomatic orbit," said Lim Eul-chul, a North Korea expert at Kyungnam University.