Putin and Kim Jong Un are getting alarmingly close, and it's put US ally South Korea in a predicament

• Russia and North Korea's historic defense pact last month sent shockwaves through global politics.

• South Korea responded by suggesting it could go all-in on supporting Ukraine with weapons.

• Putin threatened to flood North Korea with nuclear capabilities, missile tech, and more.

Russia and North Korea's newfound friendship has left key US ally South Korea in a predicament with few good options.

Seoul isn't happy about this situation, but if it decides to, as it has suggested it could, go all-in on supplying Ukraine with lethal aid, the flood gates could open, allowing Russia to give North Korea military technology, be that nuclear capabilities or missile tech.

Last month, Russian President Vladimir Putin visited Pyongyang, where he and North Korean leader Kim Jong Un further strengthened their partnership. A major focus of the summit was arms, as North Korea has been providing ammunition to Russia for its war in Ukraine in exchange for food, fuel, and potentially advanced military capabilities. What really stood out, though, was their new mutual defense pact.

Signed by both leaders, the new agreement sets the stage for one country to come to the aid of the other should it be attacked. The US has similar agreements with many of its allies.

The summit was a historic moment in Moscow's relationship with Pyongyang, signifying their closest ties since the Cold War and setting the course for uncharted territory. It meant Russia's war in Ukraine would continue to be fueled by North Korean weapons. And it set the stage for North Korea to receive military capabilities it desperately wants — potentially technologies for nuclear-powered submarines, missiles, and more.

The Russian president "is casting his lot with North Korea," Sue Mi Terry, a senior fellow for Korea studies with the Council on Foreign Relations, told Business Insider.

The play signals that "he has abandoned hopes of having some sort of relationship with the West," she explained, adding that "there is a sense that what's happening between Russia and North Korea is not a short-term tactical move."

The pact's reverberations were felt almost immediately, particularly by North Korea's neighbor to the south. Just hours after North Korean state media revealed the details of the agreement, a South Korean senior presidential official suggested it would consider sending lethal aid to Ukraine directly, a notable shift from its current policy of providing weapons via the US.

The remarks were met with a quick threat from Russia, which appeared undeterred.

"Those who supply these weapons believe that they are not at war with us," Putin said, adding that Russia reserves "the right to supply weapons to other regions," including North Korea.

His remarks essentially tell Seoul that if it goes all-in on direct support for Ukraine, Moscow can very easily make North Korea into an even more formidable adversary.

"In a sense, he's got leverage that he didn't have before by this threat to proliferate to North Korea," Victor Cha, the senior vice president for Asia and the Korea chair at the Center for Strategic and International Studies, told Business Insider. "For South Korea, it's a dilemma, it's a hard choice because they've tried very hard to support Ukraine but not become directly involved."

Due to South Korea's long-held policy barring the direct provision of lethal aid to Ukraine, it sends weapons via the US and Poland. The deal is good for Seoul, helping to establish it as a global arms supplier while letting it keep its hands relatively clean.

A shift towards directly shipping ammunition and weapons to Ukraine would thus be huge — South Korea would have skin in the game and way more at stake, as the Russian leader himself has emphasized.

Part of the dilemma is that Putin is anticipating that, regardless of what happens, South Korea will still continue to support Ukraine, Cha explained, whether that be indirectly or directly. If it's the former, then the status quo remains unchanged. And if it's the latter, then he's got the threat to give North Korea what it wants.

If they get a sense that Russia is transferring major technologies to North Korea, "then I think there's no reason for South Korea to not directly help Ukraine," Terry said.

If Russia takes that step, nothing is holding Seoul back at that point, but it risks dramatically raising tensions on the peninsula, as changes in North Korea's capabilities could warrant a response by South Korea and its allies beyond what's been suggested.

While South Korea's long been sending weapons via the US to Kyiv, there are questions about how much more aid it could provide should it change its stance. Seoul's current annual production rate is only about 200,000 155mm artillery shells, and it likely doesn't want to dip into its own stockpiles and risk shortages should it face a fight with North Korea.

The South does, however, have a significant stockpile of 105mm shells that could be beneficial to the Ukrainians. The 105s have less reach and power, but South Korea has millions of them — and they may be expiring soon, the Center for Strategic and International Studies think tank explained earlier this year.

Ultimately, perhaps South Korea's greatest concern is the conflict in Ukraine spilling over onto the Korean peninsula. With Putin supporting North Korea, tensions are higher between Pyongyang and Seoul, and the two could find themselves on the brink.

That's not a desirable outcome. The US obviously doesn't want to see its foes teaming up, but even China may find itself almost paralyzed on how to respond to a new Russia-North Korea pact, as it historically likes to keep a strong influence over North Korea and doesn't like to see Putin and Kim grow closer. "This relationship is as bad for China as it is for the United States," Cha said.

Read the original article on Business Insider