Kim could be on his way to Putin to deepen ties. Why now?

North Korean leader Kim Jong Un may travel to Russia for a summit with President Vladimir Putin, a U.S. official said, in a trip that would underscore deepening cooperation as the two isolated leaders are locked in separate confrontations with the United States.

U.S. officials also said that Russia is seeking to buy ammunition from North Korea to refill reserves drained by its war in Ukraine. In return, experts said, North Korea will likely want food and energy shipments and transfers of sophisticated weapons technologies.

A meeting with Mr. Putin would be Mr. Kim’s first summit with a foreign leader since North Korea closed its borders in January 2020. They met for the first time in April 2019, two months after Mr. Kim’s high-stakes nuclear diplomacy with then-U.S. President Donald Trump collapsed.

Russian Defense Minister Sergei Shoigu traveled to Pyongyang in July and asked Mr. Kim to send more ammunition to Russia, according to U.S. officials. Mr. Shoigu said Moscow and Pyongyang were considering holding military exercises for the first time.

It’s unclear how far Mr. Kim and Mr. Putin’s military cooperation could go, but any sign of warming relations will worry rivals like the U.S. and South Korea. Russia seeks to quash a Ukrainian counteroffensive and prolong the war, while North Korea is extending a record pace of missile tests to protest U.S. moves to reinforce its military alliances with South Korea and Japan.

Here’s a look at what Mr. Kim’s possible trip to Russia would mean:

What does Russia want from North Korea?

Since last year, U.S. officials have suspected that North Korea is providing Russia with artillery shells, rockets, and other ammunition, many of which are likely copies of Soviet-era munitions.

“Russia is in urgent need of [war supplies]. If not, how could the defense minister of a powerful country at war come to a small country like North Korea?” said Kim Taewoo, former head of Seoul’s Korea Institute for National Unification. He said Mr. Shoigu was the first Russian defense minister to visit North Korea since the 1991 disintegration of the Soviet Union.

Buying munitions from North Korea would be a violation of U.N. resolutions, supported by Russia, that ban all arms trade with the isolated country. But now that it faces international sanctions and export controls over its war in Ukraine, Russia has been seeking weapons from other sanctioned countries like North Korea and Iran.

North Korea has vast stores of munitions, but Du Hyeogn Cha, an analyst at Seoul’s Asan Institute for Policy Studies, doubted whether it could swiftly send significant amounts to Russia because the narrow land link between the countries can handle only a limited amount of rail traffic.

What does Mr. Kim want in return?

Mr. Kim’s priorities would be aid shipments, prestige, and military technology, experts said.

“It would be a ‘win-win’ deal for both, as Putin is cornered over his exhausted weapons inventory while Kim faces pressure from the South Korea-U.S.-Japan trilateral cooperation,” said Nam Sung-wook, a former director of the Institute for National Security Strategy, a think tank run by South Korea’s spy agency. “Their needs are matched perfectly now.”

Pandemic-era border closures have left North Korea with severe economic difficulties, and Mr. Kim is likely to seek supplies of food and energy to address shortfalls.

Mr. Kim will likely also trumpet expanding relations with Moscow as a sign that the country is overcoming its years of isolation. North Korean leaders have long valued face-to-face meetings with world leaders as signs of international importance and for domestic propaganda purposes.

Mr. Kim is likely also seeking Russian technology to support his plans to build high-tech weapons systems such as powerful long-range missiles, hypersonic ballistic weapons, nuclear-powered submarines, and spy satellites, said Hong Min, an analyst at Seoul’s Korea Institute for National Unification.

It’s unclear whether Russia would be willing to provide North Korea with advanced technologies related to nuclear weapons and ICBMs, Mr. Cha said. Russia has always tightly guarded its most important weapons technologies, even from key partners like China, he said.

How close could the two countries get?

Mr. Shoigu told reporters Monday that Russia and North Korea were pondering the possibility of bilateral military exercise. Earlier, South Korea’s spy agency told lawmakers that Mr. Shoigu appeared to have proposed a trilateral training exercise involving China.

Either way, it would be the North’s first joint military drills with a foreign country since the end of the 1950-53 Korean War. The country has avoided training with a foreign military in line with its official “juche,” or “self-reliance,” philosophy.

Kim Taewoo, the former institute director, said expanding South Korea-U.S.-Japan security cooperation could prompt Kim Jong Un to break that taboo and hold drills with Russia and China for the first time.

But Mr. Nam, who is now a professor at Korea University, said North Korea won’t likely accept the offer, as it could leave North Korea even more dependent on China and Russia.

Park Won Gon, a professor at Seoul’s Ewha Womans University, said it’s too early to predict what Mr. Kim’s diplomacy could yield beyond making a show of defiance toward the United States.

“In any case, North Korea and Russia need to show that they’re working together, that they’re stepping up this cooperation,” Mr. Park said. “There clearly are practical areas of cooperation, and also some symbolic aspects they want to show to the United States.”

This story was reported by The Associated Press.