U.S. State Department spokesperson Matthew Miller expressed deep concern over Russian President Vladimir Putin's comments on Thursday about potentially supplying weapons to North Korea following a defense pact with Pyongyang.

Putin, after visiting North Korea, indicated that such an arms supply would be a reciprocal response to the West arming Ukraine. He also warned South Korea against arming Ukraine, suggesting it would provoke a painful response from Moscow.

Miller emphasized the destabilizing effect such actions could have on the Korean Peninsula and potential violations of U.N. Security Council resolutions, which Russia has supported. The defense pact between Putin and North Korean leader Kim Jong Un, signed on Wednesday, commits both nations to immediate military assistance if either faces armed aggression.

White House national security spokesperson John Kirby noted the predictable nature of this development, linking it to Russia's desperation for foreign assistance. He mentioned ongoing concerns about Russia supporting North Korea's missile and nuclear programs.

U.S. officials believe North Korea seeks advanced military technologies from Russia, while Western nations allege North Korea has already supplied Russia with artillery shells and ballistic missiles, claims both countries deny.

Russia's veto of extending a U.N. body monitoring sanctions on North Korea has drawn Western condemnation.

Kirby also suggested that the Russia-North Korea pact would concern China, potentially undermining Beijing's influence over its neighbors and impacting China's strategic ambitions.

Analysts, such as former Obama administration Asia specialist Evan Medeiros, warned that the pact could destabilize the region by providing North Korea with advanced military capabilities and possibly emboldening Kim Jong Un. There are fears this could lead to renewed nuclear testing by North Korea.

In response, Senators Lindsey Graham and Richard Blumenthal reiterated their call for the U.S. to designate Russia as a state sponsor of terrorism, a proposal the Biden administration has not yet endorsed due to concerns over diplomatic repercussions. Russia has warned that such a designation could severely damage or even sever diplomatic ties with the U.S.