(Bloomberg) — Russian President Vladimir Putin said that he can’t exclude providing North Korean leader Kim Jong Un with high-precision weapons in response to Western military assistance for Ukraine.

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“We reserve the right to supply arms in other regions of the world,” Putin said late Thursday at a press conference in Hanoi. “Bearing in mind our agreements with the Democratic People’s Republic of Korea, I don’t rule this out.”

The two leaders signed a deal Wednesday to provide immediate military aid if one of them is attacked, rekindling an agreement dating back to the Cold War when the Soviet Union was a main backer for Pyongyang. Kim said the agreement elevated relations with Russia to an alliance.

The pact, dubbed the Comprehensive Strategic Partnership Treaty, also says Russia and North Korea will work together to strengthen their defense capabilities, while expanding cooperation in trade and investment.

The warning is likely to unnerve the US and its partners and ratchet up tensions. It also raises the risks for Western countries responding to provocations from Moscow and Pyongyang.

“Westerners give arms to Ukraine and say ‘we don’t control how they are used afterward,’” Putin told reporters in response to a question on the provision of advanced arms. “We can also say the same.”

South Korea, earlier on Thursday, said it would reevaluate its policy of prohibiting the export of lethal aid to countries such as Ukraine and expressed concern over the pact between Moscow and Pyongyang. Putin told reporters that it would be a mistake for South Korea to provide weapons to Kyiv.

The US, South Korea and Japan have accused Kim’s regime of sending munitions and ballistic missiles to aid Putin in his war on Ukraine. Moscow and Pyongyang have denied the arms transfers despite ample evidence showing them taking place.

Putin also said Russia was considering changes in its nuclear doctrine in response to discussions in the West about “lowering the threshold for the use of nuclear weapons” and the development of less powerful arms. Russia recently held combat drills to practice the use of tactical nuclear weapons.

The Russian leader has repeatedly brandished the threat to use nuclear weapons since the start of his February 2022 invasion, drawing condemnation from the US and its North Atlantic Treaty Organization allies.

Still, Putin said Russia doesn’t need to introduce the idea of a so-called preventative strike. “In a retaliatory strike, the enemy will be guaranteed to be destroyed,” he said.

Putin was in North Korea on his first visit in 24 years before traveling to Vietnam.

(Updates with additional comments from Putin from the ninth paragraph.)

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