A laser beam downs drones by heating up and “frying” their electronics – each invisible, soundless “shot” is more precise and less costly than an air defence missile.

Hanwha Aerospace, a South Korean defence company, has fire-tested and is about to start mass-producing the world’s first-ever optical fibre laser weapon.

And Hanwha is ready to supply it to Ukraine if Seoul lifts a ban on the export of lethal weapons to Kyiv “in light of North Korean military activities”, South Korean President Yoon Suk Yeol said in late October.

His statement followed North Korea’s deployment of about 10,000 soldiers to western Russia, becoming the first foreign power to step into the Russia-Ukrainian war.

However, the US president-elect may stand in the way.

Donald Trump and his fledgling administration members have repeatedly said that they want to limit US military aid to Ukraine – or even stop it altogether.

Seoul may have to follow suit, two South Korean officials told Bloomberg on Thursday.

However, a member of the Ukrainian delegation that visited Seoul earlier this month doubts it.

“I don’t think they will refuse. They seemed rather independent and self-sufficient in their diplomatic and military politics,” Roman Bochkala, co-founder of a Ukrainian charity fund that delivers arms and other crucial supplies to the front line, told Al Jazeera.

“It’s paramount to [South] Korea to maximally compensate for the potential danger of real combat experience the North Korean army might get,” he said.

Another Ukrainian analyst agreed – but said that Seoul may not sell other lethal weaponry to Kyiv.

“Such [weaponry] will most likely not be limited, but we will have to pay for it,” Kyiv-based analyst Aleksey Kushch told Al Jazeera. “But Seoul will hardly make artillery shells for us. And won’t send any tanks.”

South Korea has reportedly supplied hundreds of thousands of artillery shells via the United States and pledged a $2.3bn low-interest loan to Kyiv.

Seoul is the world’s 10th-largest arms exporter, and its clients already include four nations that border Russia – Poland, Estonia, Finland and Norway.

But Kyiv may be the first to receive the lasers in what could significantly knock down the price of Ukraine’s air defence.

“[South] Koreans swear that their laser will fry enemy drones with an almost 100 percent guarantee, destroying engines or other electronic equipment within 10-20 seconds,” Bochkala said.

The South Korean systems will supplement Patriots, advanced air defence systems that cost $1bn each and need $4m missiles that are often spent on downing Russia’s $50,000 drones.

The laser needs nothing but electricity – and could be deployed to the Ukrainian cities that have no Patriots or similar Western or Taiwanese air defence systems.

“There are never too many good friends. And South Korea may become one for Ukraine,” Bochkala said.

North Koreans in Kursk

In early August, Ukrainian forces seized a chunk of Russia’s westernmost Kursk region – and have held on to most of it.

Kyiv hoped that Moscow would deploy troops from the front lines of the eastern Ukrainian region of Donbas to repel the surprise invasion that roiled the Russian populace.

“Many didn’t give a damn about the war until Ukrainians entered Kursk. Now, they’re volunteering in droves, because the motherland is in danger,” a Moscow resident told Al Jazeera on condition of anonymity.

But it took the Kremlin weeks to start the counteroffensive as it kept on pushing in Donbas, taking several crucial towns and villages.

North Korean soldiers joined the fray earlier this month, according to Western and Ukrainian intelligence and officials.

“It significantly boosts the enemy’s potential,” Lieutenant-General Ihor Romanenko, former deputy head of Ukraine’s general staff of armed forces, told Al Jazeera.

However, Moscow decided not to concentrate the North Koreans in one place instead deploying small groups to Russian units.

“They are not collected in one fist, which would have been more effective had there been a [North Korean] division or a brigade,” Romanenko said.

With some 1.3 million servicemen and millions of reservists, North Korea has one of the world’s largest armies.

It is armed with Soviet-era weaponry or its domestically produced replicas.

And though the Kursk deployment may look sensational, North Korean leader Kim Jong Un in fact “mirrors” what a South Korean leader did half a century ago, according to analyst Kushch.

Between 1964 and 1973, when South Korea was poorer and less industrialised than the pro-Communist North, South Korean President Park Chong-hee deployed some 350,000 soldiers to Washington’s war Vietnam – along with tens of thousands of workers.

In exchange, he secured multibillion-dollar US investments, credits and technology transfers that helped turn South Korea into one of the world’s most technologically advanced and affluent nations.

Vietnam accused South Koreans of war crimes, but Park paid no heed as the economic boom helped him cement his grip on power.

‘Putin will reserve a Korean trump card’

Kim Jong Un is equally unceremonious as Moscow props his nation’s economy with billions of dollars paid for arms and ammunition, discounted supplies of energy, food and technologies.

Kim’s Kursk deployment may become a powerful bargaining chip in the ceasefire talks with President-elect Donald Trump’s future administration.

“Putin will reserve a Korean trump card up his sleeve before future talks with Trump – or for the final attack in the Kursk region that for now seems to be maximally delayed,” Kushch said.

Earlier this week, Ukrainian troops in Kursk repelled a massive Russian advance and reported first losses among North Koreans.

The deployment may look like Putin’s weakness amid reports of a dire shortage of manpower, but the consensus in Russia is: “Let them fight instead of us,” according to Volodymyr Fesenko, head of the Kyiv-based Penta think tank.

Meanwhile, the rapprochement between Moscow and Pyongyang likely irks Beijing, North Korea’s main backer, according to Fesenko.

“North Korea is eluding China’s monopolistic influence, and Russia’s clout in Beijing’s own back yard is on the rise,” he told Al Jazeera.

There is also a significant risk of escalation on the Korean Peninsula as “after battle-testing his troops in a real war, Kim may get excited by the smell of blood,” Fesenko said.