SEOUL—For more than four years, Kim Jong Un has stayed inside his country’s borders, focused on a deadly virus, a stifled economy and a corrupt elite.

       Now, the North Korean leader, U.S. officials said, could be planning his first foreign trip to Russia for a meeting with Vladimir Putin. Talks could advance between the two countries about ammunition sales that could replenish Russia’s stockpile for its Ukraine war.

       U.S. officials say the get-together between Kim and Putin could occur next week in the eastern Russian city of Vladivostok, which was the site of the two leaders’ first and only meeting in April 2019.

       Russia could potentially provide aid to North Korea, which is suffering its worst food shortage in decades, after the impoverished nation kept its borders shut during the Covid-19 pandemic. Kim’s regime can also use his return to overseas statesmanship in its propaganda to show it has moved on from pandemic isolation. And with coordination deepening between Washington, Tokyo and Seoul, any military strengthening with Moscow could serve as a reminder that the isolated regime has powerful friends.

       “North Korea feels really threatened," said Artyom Lukin, an expert on Russia-Asia relations and professor at the Far Eastern Federal University. “Kim Jong Un understands well how weak North Korea is, even with its nuclear weapons, vis-à-vis the U.S. alliance with South Korea and Japan."

       On Monday, South Korea’s spy agency told lawmakers that Russia had also proposed conducting naval exercises with North Korea and China during a recent visit to Pyongyang by Russian Defense Minister Sergei Shoigu.

       Russia said it had nothing to say on a potential summit, while North Korea hasn’t publicly commented on the matter.

       U.S. officials previously accused North Korea of shipping infantry rockets and missiles to the Wagner Group, the Russian paramilitary force, among other attempts to replenish lethal aid—assertions that Moscow and Pyongyang have denied.

       Putin has plenty to gain from talking to Kim. In the past, North Korea has sent thousands of workers abroad—many of them to Russia. Kim’s regime could agree to send more at a time when Russia is suffering from high labor shortages, especially in Siberia and its far east.

       The potential meeting would come as Ukraine’s forces have made progress piercing through some Russian fortifications in the south. Russia’s forces are facing shortages of artillery shells and even basic munitions could help its position on the battlefield, Western officials have said. Pyongyang could help stabilize munitions supplies as Moscow scales up production.

       But North Korea has some limitations in its ability to supply weaponry. North Korea has more than 300 munitions factories capable of producing weapons, though years of international sanctions have affected operations due to a lack of raw materials or replacement parts, South Korea’s defense ministry said.

       North Korea isn’t well positioned to supply modern lethal aid, weapons experts say. Much of Pyongyang’s stockpiles are Soviet-era missiles. The country hasn’t begun mass production of the advanced weaponry that it has revealed in recent years.

       Any arms deal between Pyongyang and Moscow would violate United Nations Security Council resolutions, as would any increase in North Korean laborers sent to Russia.

       The sanctions are limited in effect as long as China and Russia block the international community from putting additional pressure on North Korea, leaving the U.S. with no option but to strengthen military cooperation with its allies, said Chun In-bum, a former special forces commander in the South Korean army.

       The lack of recourse against North Korea has helped catalyze increased coordination by the U.S., Japan and South Korea, which have agreed to knit together their missile-radar systems and boost joint military exercises.

       “Unfortunately, I don’t see any viable nonmilitary actions left," Chun said. “Ironically, the North Koreans are fostering trilateral cooperation."

       Putin and Kim have expressed appreciation for one another, as much of the West shunned the Russian leader for the invasion of Ukraine and Kim for his spree of missile tests. In June, Kim promised in a letter to keep “holding hands firmly" with Putin. The two leaders have exchanged a series of letters. Last month, Putin wrote to Kim, pledging to bolster ties in all fields.

       High-level visits between the two countries began about six weeks ago, when Shoigu led a Russian delegation to Pyongyang for a tour at a defense expo and a North Korean military parade. That visit, U.S. officials said, was aimed at convincing Pyongyang to sell artillery ammunition to Moscow. Since then, Russian officials have traveled to Pyongyang for follow-on discussions, National Security Council spokesman John Kirby said.

       Kim hasn’t left North Korea since June 2019, when he stepped over the Korean Demilitarized Zone to meet with then-President Donald Trump. The visit capped a string of overseas exchanges with Trump, Putin, Chinese leader Xi Jinping and the heads of South Korea, Vietnam and Singapore.

       Write to Timothy W. Martin at Timothy.Martin@wsj.com and Dasl Yoon at dasl.yoon@wsj.com

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