BEIJING — China shares a “no limits partnership” with Russia and remains a crucial supporter to North Korea. Yet as its two neighbors — isolated by the U.S. and the West — forge closer ties, Beijing appears to be keeping its distance.

North Korean leader Kim Jong Un and Russian President Vladimir Putin rattled global geopolitics last week by signing a comprehensive strategic partnership agreement that includes a mutual defense pact, bringing the two nuclear-armed states closer than they have been since the Cold War.

Putin’s rare visit to North Korea, his first in 24 years, comes as he is seeking greater support from Pyongyang for his war in Ukraine. U.S. officials have told NBC News that in exchange for providing Russia with badly needed munitions, North Korea could get Russian assistance on the military technology it needs to advance its nuclear, missile and satellite programs, including weapons capable of reaching the continental United States.

The elevation in relations, which Kim described as an “alliance,” also sends a message to China, North Korea’s biggest lifeline, that Pyongyang has another powerful friend in Moscow.

“Kim Jong Un has a number of things to gain from this at a strategic level,” said John Delury, professor of Chinese studies at Yonsei University in Seoul. “This gets China’s attention and makes Xi Jinping pay a little bit more heed perhaps to what’s going on across his border.”

The mutual defense treaty, which resuscitates a Cold War-era agreement between Russia and North Korea to provide each other with military assistance if either should face “aggression,” comes at a time when China has accused the U.S. of similar bloc-building.

Experts say the U.S. is likely to respond to the pact by further strengthening its security ties with regional allies South Korea and Japan, adding to Beijing’s sense of U.S. military encroachment in the Asia-Pacific.

In a statement released on Sunday, the U.S., South Korea and Japan said they condemned “in the strongest possible terms” the deepening military cooperation between Russia and North Korea but that they remained open to talks with the North.

U.S. and other officials are also watching to see how China responds to Russia’s overtures toward North Korea.

“We’ve got someone else who’s kind of nudging in now, so that may drive a little bit more friction” between China and Russia, Gen. Charles Q. Brown Jr., chairman of the Joint Chiefs of Staff, told reporters on Sunday, according to Reuters.

China has said very little about the growing ties between Putin and Kim, two of President Xi Jinping’s closest partners, both of whom have come to rely heavily on Beijing for economic and diplomatic support to offset the sting of international sanctions.

A spokesperson for the Chinese Foreign Ministry declined to comment on the Russia-North Korea pact on Thursday, saying it was a matter between those two countries.

China, Russia and North Korea share a hostility to the U.S.-led international order, which was underlined last month during Putin’s state visit to Beijing. But China is less globally ostracized than the other two countries and is reluctant to jeopardize its relations with Europe, South Korea, Japan and others by becoming part of any trilateral “authoritarian axis.”

“What China has been very careful and clear about is to frame the relationships among the three countries as three bilateral relations rather than one trilateral relation,” said Yun Sun, director of the China program at the Stimson Center, a think tank in Washington.

“China wishes to keep its options open rather than being bogged down by Russia and North Korea.”

Xi has worked meticulously to position China as a global player, walking a tightrope on the Ukraine war by not condemning Russia’s invasion, which has put him at odds with the West. Unlike in the case of North Korea, U.S. officials say there is no evidence that China has directly offered weapons to Putin, though several Chinese companies have been sanctioned over trade in dual-use components that could have military applications.

Both North Korea and Russia deny the transfer of arms for use in Ukraine, which would be in violation of United Nations Security Council resolutions that Russia has supported in the past.

Further destabilization on the Korean Peninsula would be yet another headache for Xi, who is already struggling with a number of domestic issues, including an economic slowdown.

China would also not welcome the advances in Kim’s nuclear weapons and missile programs that Russian technology might facilitate, nor would it want to see South Korea seek to develop its own nuclear weapons in response to the growing North Korean threat.

North Korea might “make use of its ‘generosity’ to ask for some military technological transfer from Russia in return,” said Zhou Bo, a senior fellow at the Center for International Security and Strategy at Tsinghua University in Beijing and a retired senior colonel in the Chinese People’s Liberation Army.

“This raises the question of how the situation might have a chain reaction in Northeast Asia.”

Putin’s visit to Pyongyang last Wednesday was his second summit with Kim in less than a year, after the North Korean leader visited Russia’s far east in September. Kim and Xi have not met since 2019.

From the moment Putin set foot on the red carpet at Pyongyang International Airport, where he was greeted and embraced by Kim, the choreography of the historic visit was set into motion. As the two leaders greeted officials, held talks and exchanged gifts, they did not leave each other’s side.

Putin and Kim even took turns behind the wheel of an Aurus limousine airlifted from Russia for the occasion in a highly produced “Top Gear”-style video released by North Korean state media.

All of it seemed designed to telegraph a message: that the two leaders — shunned by much of the world — were not without friends.

“They’re leaning quite heavily into each other to a degree not seen in decades and that sort of tilts all the other balances,” Delury said.

“China is actually wary of what’s going on.”