WASHINGTON -- The United States takes its defense commitment to South Korea "very, very seriously," a White House official said Thursday, following Russia's threat to arm North Korea if South Korea sends lethal assistance to Ukraine.

John Kirby, National Security Council coordinator for strategic communications, said the US is grateful for the support South Korea has already provided to Ukraine.

"I would just remind that we have a treaty alliance with South Korea. We take that commitment very, very seriously," Kirby told a press briefing when asked to comment on Russia's threat to arm North Korea.

The Russian threat came after South Korean President Yoon Suk Yeol said South Korea may be obliged to provide more than humanitarian assistance to Ukraine if Russia conducted large-scale attacks on civilians.

The Kremlin said that providing military aid to Ukraine would mean "Seoul becoming involved in the conflict to a certain extent," and threatened to arm North Korea if South Korea armed Ukraine.

"We are grateful for the support that South Korea has already provided Ukraine," Kirby said, noting Seoul has already provided some $100 million worth of humanitarian aid assistance to the East European country.

"And of course, they've been very vocal in supporting Ukraine and they've been very vocal in speaking out against Russia's aggression," he added, calling South Korea a "terrific ally, terrific friend."

Kirby also highlighted President Yoon's upcoming state visit to the United States, during which he said Yoon and President Joe Biden will discuss a wide range of issues, including the Russian war in Ukraine.

"I have absolutely no doubt that they will talk about a range of challenges, not just in the Indo-Pacific but across Europe and in Ukraine," he told the press briefing.

Yoon is set to arrive here on Monday, becoming the first South Korean head of state to make a state visit to the US since 2011. He and Biden will hold a bilateral summit on Wednesday, followed by a state dinner to be hosted by Biden later that day.

Topics for the leaders will also include North Korea's continued provocations, as well as challenges posed by China, according to Kirby.

"I know of no conversation that we ever have with our allies in the Republic of Korea where we don't talk about the threats posed by North Korea to the peninsula and to the region," he said when asked about the summit, referring to South Korea by its official name.

"And I know of no discussion that we have with those very important allies when we also (don't) talk about the challenges posed by China in the region and globally, and I fully expected that both will be will be matters of discussion," he added. (Yonhap)