North and South Korea are locked in a dangerous arms race. Putin may be about to make this worse.

• North Korea and South Korea are in an intensifying arms race.
• North Korea has launched a series of missile tests.
• Russia's new alliance with North Korea could worsen the situation.

North Korea on Monday claimed it had tested a new weapon capable of far greater destruction than the ballistic missiles in its arsenal.

The Hwasong-11Da-4.5, which has a 4.5-ton warhead, follows South Korea's development of multi-ton warhead ballistic missiles, designed as "bunker busters" that can take out North Korean nuclear bases, amid an intensifying arms race on the peninsula.

The South Korean military called the announcement a "deception," claiming North Korea had botched a test in which a missile crashed near Pyongyang.

The situation could get more dangerous in the wake of Russian President Vladimir Putin's new security alliance with North Korean leader Kim Jong Un.

The UN seeks to contain North Korean aggression

For decades, the UN Security Council, of which Russia is a permanent member, has sought to restrict North Korea's nuclear weapons program, cutting off access to key technology and the global economy.

Russia appeared wary of the potential threat North Korea posed on its eastern border and worked with countries, including the US, to isolate Kim — but the Ukraine war has changed that.

Desperate for new supplies of ammunition and artillery for his army, Putin has found a willing new supplier in North Korea.

According to reports, North Korea has supplied Russia with up to 3 million shells for its campaign in Ukraine , along with ballistic missiles used to target Ukrainian cities.

In turn, Russia is helping North Korea break its diplomatic, economic, and military isolation.

It has increased food and fuel exports to North Korea and vetoed the renewal of a UN panel that monitors the sanctions against the country.

The Kremlin is also suspected of handing North Korea vital satellite technology that the rogue state could use to monitor US allies in the region and, if there were a war, target their military assets more effectively.

So far, Russia seems to have stopped short of providing North Korea with direct military support, though it has pledged to come to its aid if attacked.

But analysts at the Center for Strategic and International Studies are concerned that Kim could drive a "hard bargain" and demand more high-end nuclear and missile technology.

"North Korea would benefit from fielding a nuclear weapons force that could evade US missile defenses with high-end intercontinental ballistic missiles and nuclear submarines," they wrote in an article published June 20.

North Korea may have exaggerated how well Monday's test went, but Russia's alliance is definitely enhancing the threat the country poses to the delicate security balance in East Asia.

Improved missile technology could, in theory, enable North Korea to evade US missile defense systems and strike the US mainland, undermining the US's security pledge to South Korea.

If North Korea comes closer to being able to strike the US, it could fuel "skepticism about American nuclear guarantees" and, in turn, "spark a renewed push by South Korea to develop its own nuclear deterrent," wrote analysts from the Wilson Center in April.

South Korea's government has said it could send weapons to Ukraine in response, and Voice of America reported Monday that some South Korean politicians are questioning the effectiveness of America's nuclear deterrent.

Politician Na Kyung Won said last week that deterrence was "currently working" but "does not guarantee the capacity to respond to the future changes in the security environment," the outlet reported.