The South Korea-US alliance is not just between the two countries' presidents, but one between their governments and between their people, a State Department spokesperson said Monday, stressing that there is no "diminution" in the bilateral partnership in the wake of President Yoon Suk Yeol's impeachment.

Matthew Miller, the spokesperson, made the remarks amid lingering concerns that Yoon's impeachment could affect policy coordination between Seoul and Washington at a time when security threats continue from North Korea's advancing nuclear and missile programs and its deepening military alignment with Russia.

"There will be no diminution in the alliance between the United States and the Republic of Korea," Miller told a press briefing, referring to South Korea by its official name.

"That alliance is not just an alliance between presidents. It is an alliance between governments and an alliance between peoples and our commitment to that alliance remains ironclad," he added.

Miller noted that over the past few weeks, South Korea demonstrated its "democratic resilience."

"That is democratic resilience that was hard won several decades ago, and we've seen them follow peacefully a process that was laid out by the Republic of Korea's Constitution," he said.

"We are ready to continue to work with the acting president and the government of the Republic of Korea in the same way that we were acting and cooperating with President Yoon."

In a separate online press briefing, White House National Security Communications Adviser John Kirby said the US will stay committed to the alliance with South Korea, which he portrayed as "incredibly healthy."

"A significant ally remains a significant ally -- an alliance that is incredibly healthy now, (which is) the result of these last four years of really working on our alliances and partnerships in the Pacific," he said.

Kirby mentioned that President Joe Biden had a phone call with South Korea's acting President Han Duck-soo over the weekend to reaffirm the US' commitment to the South Korean people and the alliance.

He refused to comment on legal issues surrounding Yoon.

"Your question about whether he should be charged with insurrection ... those kinds of things are for South Korean officials, South Korean legislators, the South Korean people to determine, not the United States," he said.

"All I will say is that as the president said to acting President Han Duck-soo, this is an important relationship for us. It is a terrific alliance. The United States is going to stay committed to it."

South Korea's National Assembly impeached Yoon last week over his botched martial law attempt, suspending his presidential duties until the Constitutional Court decides whether to reinstate or unseat him from office. Prime Minister Han has taken over as acting president. (Yonhap)