The Russian invasion of Ukraine has provided an opportunity for North Korea, which has strengthened ties with Moscow and become one of its most vocal supporters.

Pyongyang wants to send laborers to the Russia-controlled regions of eastern Ukraine, Donetsk and Luhansk, to provide the Kim regime with much-needed foreign revenue. Russian President Vladimir Putin has promised to provide advanced weapons and military equipment to allies, even as North Korea pursues new assets such as hypersonic missiles. Moscow can also increase cross-border food and aid trade and use its seat on the United Nations Security Council to block any tougher sanctions against North Korea.

North Korea was one of only five countries in March to vote against a United Nations resolution demanding that Russia end its invasion of Ukraine, blaming the root cause on the US and its allies’ “hegemonic policy.” North Korea was one of the first countries to recognize Donetsk and Luhansk as independent republics in July, prompting Kiev to cut diplomatic ties with Pyongyang.

The United Nations barred North Korean laborers from working abroad after a 2019 deadline, effectively cutting off the Kim regime’s main source of foreign income. Russia was one of the largest hosts of North Korean foreign workers prior to the clampdown, with approximately 30,000 such people. North Korean workers were appealing because Russian companies advertised their wages as being 30% to 50% lower than those of other migrants in the region, who typically came from Uzbekistan and Kyrgyzstan.

Russia is likely to maintain that Donetsk and Luhansk are independent regions that are not subject to international sanctions because they are not members of the United Nations. During a meeting earlier this month with a Donetsk envoy, North Korea’s ambassador to Russia revealed plans to send laborers to the region once the Kim regime’s Covid-19 border restrictions were lifted.

According to Alexander Matsegora, Russia’s Ambassador to North Korea, in an interview with the Russian newspaper Izvestia last month, North Korean workers could help restore facilities in Donetsk that were damaged by fighting in the Ukraine conflict.

Mr. Matsegora stated that North Koreans are also interested in purchasing spare parts manufactured in the region and rebuilding their production facilities. The potential transactions foreshadow other efforts that could violate UN sanctions.

The Biden administration has offered to meet with North Korea at any time, but Pyongyang has turned it down. In nearly three years, the two countries have not held formal nuclear talks.

The growing Moscow-Pyongyang alliance has reached the highest levels. According to Pyongyang state media, the leaders of Russia and North Korea exchanged letters earlier this month. Mr. Putin expressed a desire to expand relations, while Kim Jong Un stated that bilateral ties had reached a new high “in the common front for frustrating the hostile forces’ military threat and provocation”—a term frequently used to describe the United States and its allies.

In early 2020, the Kim regime was one of the first to seal off its borders after Covid-19 was discovered in neighboring China. North Korea resumed some cross-border trade activity earlier this year, but an outbreak forced the impoverished country to close down again.

However, Mr. Kim declared a public-health victory this month and promised to relax measures from their maximum levels. According to Anthony Rinna, a specialist on Russia-North Korea relations at the Sino-NK research group, a website focused on China and North Korea, once cross-border trade resumes, Russia could illegally provide North Korea with coal or export prohibited luxury goods.

Mr. Putin met Mr. Kim in person for the first time in 2019, just months after the North Korean leader failed to broker a nuclear deal with former US President Donald Trump in Vietnam. Though he did not specifically mention North Korea, Mr. Putin pledged at a recent security conference to “consistently strengthen the national armed forces and other security structures” by providing advanced weapons and military equipment to its allies.

The Soviets assisted in the construction of a reactor at Yongbyon, which has since become North Korea’s main nuclear facility. Russian scientists provided North Korea with fuel technologies in the 1990s, which aided Pyongyang’s missile development program. According to a 2017 report by the International Institute for Strategic Studies, a London-based think tank, the liquid-propellant engine used during intermediate and intercontinental missile launches is based on technology developed by the Soviet Union.