(Bloomberg) -- North Korean leader Kim Jong Un pledged to “unconditionally support” Russia in its invasion of Ukraine at talks with President Vladimir Putin in Pyongyang that emphasized deepening ties amid US concerns about arms supplies to the Kremlin’s war machine.

The two leaders signed a deal Wednesday to come to the other’s aid if attacked, rekindling an agreement dating back to the Cold War, when the Soviet Union was the main backer for Pyongyang. Kim said the agreement elevated relations with Russia to an alliance.

“I would like to stress that the birth of this treaty, the most powerful treaty in the history of North Korea-Russia relations, was possible thanks to President Putin’s outstanding foresightedness and bold determination,” Kim said at a news briefing after the talks.

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While Kim added the military deal is for defensive purposes, it raises the risks for the US and its partners in responding to provocations from Moscow and Pyongyang and is a symbol of their defiance against Western powers.

“Russia hasn’t been an active player in Asia for a long time, both militarily and diplomatically. But its upgraded and comprehensive relationship with North Korea means that Asia has now quickly woken up to a threat by another big power,” said Duyeon Kim, a Seoul-based adjunct senior fellow at the Center for a New American Security. “An inadvertent conflict based on miscalculation could potentially escalate to a regional or world war.” 

The accord was signed during the Russian leader’s first visit to North Korea in 24 years. Kim said Russia is playing a critical role in keeping a strategic balance in the world, while Putin said he hoped Kim will visit him in Moscow.

“Today we have prepared a new fundamental document that will form the basis of our relations for the long term,” Putin told the North Korean leader. “We highly appreciate your consistent and unwavering support for Russian policy, including in the Ukrainian direction.”

Kim said his country would “unwaveringly, unconditionally support Russia’s every policy regardless of any complication on the international geopolitical situation going forward.”

The North Korean leader said the Comprehensive Strategic Partnership Treaty agreed with Putin would strengthen cooperation between the two countries, including in the economic, political and military spheres.

Putin’s visit came hours after the first high-level security talks between China and South Korea in about nine years on Tuesday. After the Soviet collapse and the rise of China as an economic power, Beijing has been Pyongyang’s main benefactor. But the deepening relationship between Kim and Putin may be leading to a realignment.

“This won’t be exactly what China would have wanted as more military tension in the region would mean an increased US military presence in the region,” said Lim Eul-chul, a professor at Kyungnam University’s Institute for Far Eastern Studies in Seoul. “It gives another reason for the US to strengthen its trilateral partnership with South Korea and Japan.” 

Putin’s formal visit kicked off with a welcoming ceremony at Kim Il Sung Square in central Pyongyang involving a red carpet, white horses, balloons and cheering crowds holding flowers and flags of the two countries, video showed. Massive portraits of the two leaders were hung side by side at the plaza as the ceremony took place. 

The trip comes after Kim traveled to Russia in September, which as satellite imagery later showed was followed by a massive growth in arms transfers. Putin last visited Pyongyang in 2000 as Russia’s president. 

Moscow and Pyongyang have denied the arms transfers despite ample evidence showing them taking place. 

US Secretary of State Antony Blinken said Tuesday in Washington that Russia is trying “in desperation to develop and to strengthen relations with countries that can provide it with what it needs to continue the war of aggression it started against Ukraine.” Pyongyang has provided Moscow with “significant munitions” and other weapons for use in Ukraine, he said.

North Korea possesses some of the largest stores of artillery and weapons that are interoperable with Soviet-era systems deployed on the front lines in Ukraine.

In return for the munitions from Kim’s regime that could reach as high as nearly 5 million artillery shells, Russia has sent to North Korea technology to help in its plans to deploy an array of spy satellites, South Korean Defense Minister Shin Wonsik said in a recent interview with Bloomberg News. Russia will likely send military technology to Kim, increasing Pyongyang’s threat to the region, he said. 

Putin will travel to Vietnam later Wednesday after concluding talks with Kim, according to the Kremlin.

--With assistance from Shinhye Kang.

(Updates with analyst comments in fifth, 11th paragraphs.)

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