Vladimir Putin and Kim Jong Un may each have something the other wants -- a dangerous combination as far as the US is concerned.

A meeting that may be in the works between the Russian and North Korean autocrats could have an impact on the war in Ukraine, complicate Washington's repeatedly failed efforts to rein in Pyongyang's nuclear program, and play into the wider geopolitical chess game unfolding in the Pacific in which China is the major player.

Washington has reacted to the possibility of the meeting -- which could possibly take place after Kim climbs aboard his armored train headed for the Russian far east -- by mocking Putin, warning North Korea and trying to work out what it might mean.

Russia may be looking to Kim to replenish its ammunition and artillery supplies as the war in Ukraine grinds into another bloody winter. Pyongyang is also adept at drone and missile technology. Kim, meanwhile, knows that Russia is a longtime and sophisticated nuclear power whose expertise could help his own expanding program. It's also a big oil supplier, and North Korea and Russia are both living under punishing Western sanctions and restrictions on their access to the global market. If they can help each other ease the pain of blockades, they may be able to do business.

Plus, for the North Korean leader, the propaganda value of his impoverished country helping to shore up the much bigger Russia could be valuable. And he'll get Washington's attention after a years-long diplomatic freeze following the flurry of praise and summitry of former US President Donald Trump's administration.

As it often has during the Ukraine war, Washington is trumpeting information from its intelligence agencies to foreshadow and discredit Putin's moves before they happen. When it comes to cruel sarcasm, there's no better practitioner than Rahm Emanuel, the US ambassador to Japan and an acerbic political operative. If the overarching goal of Russia's invasion of Ukraine was to recreate Moscow's empire, Emanuel told CNN "that empire is now dependent on North Korea, it is dependent on Iran -- two isolated countries, two countries that are seen as pariahs. That tells you how much of a failure this war is."

At the White House, national security adviser Jake Sullivan said that the US is trying to work out whether North Korea could make a significant difference to Russia's war effort. "We have asked our intelligence community that ... question. It is a good question. Our visibility into both the question of quantity of stocks and then, of course, quality of stocks is somewhat constrained," Sullivan said, adding: "I think there is an open question about how much materiel and what the quality of the materiel is that could be provided if it were to be provided."

Sullivan warned that selling arms that Russia could use to attack grain silos or the heating infrastructure of major Ukrainian cities would not reflect well on North Korea. But moral arguments won't move Kim, who keeps his population locked in a vast prison camp wracked by repression and famines.

While the US is dismissive of the possible Kim-Putin meeting, both leaders have the capacity to make trouble for Washington. Russia once joined the US in a multi-national effort to constrain Pyongyang's nuclear and missile programs, but that clearly isn't likely anymore as Putin seeks to puncture US influence around the globe. That means the North's arsenal of mass destruction will remain an increasingly grave threat to US national security.

There's a political dimension here as well. If North Korea is able to offer Putin significant military help, it would bolster Russia's hopes of prolonging the war just at the moment when Ukraine's slow-to-start offensive seems to be beginning to make some real gains. If the war stretches deep into the US election year, Putin could increase the political pressure on President Joe Biden amid growing public questions about Washington's multibillion-dollar lifeline for Ukraine. This skepticism is being fueled by Trump's warnings that Ukraine should be cut loose and that he'd end the war -- on terms likely favorable to Russia -- if he wins the 2024 election.

A Putin and Xi Jinping meeting would also cement concerns that the world's tyrants are combining in an anti-US alliance. Putin's friendship with the Chinese leader has worried the US, although Beijing may not have offered quite the assistance that the Russian leader might have hoped for -- one reason he may be turning to North Korea for military supplies. Russia is of course also a Pacific power and could further destabilize an already tense geopolitical theater there that represents America's most vexing national security challenge.