Acting President Han Duck-soo and National Assembly Speaker Woo Won-shik on Sunday pledged close cooperation and communication between the Cabinet and the parliament to achieve stable management of state affairs.

In line with the latest vow, Woo called for Han to swiftly form a joint consultative body between the government and the Assembly to run state affairs.

"The government will closely communicate with the Assembly ... (we) will make efforts to bridge the gaps in the opinions with a willingness to listen and with a humble attitude," Han said in the meeting.

"I hope that under the sensible leadership of the Assembly speaker, stabilization of the state affairs will be swiftly achieved with the cooperation of the ruling and the opposition parties and the government," he added.

The talks came a day after the passage of an impeachment motion against President Yoon Suk Yeol in the National Assembly on charges of insurrection tied to his botched declaration of martial law on Dec. 3. Prime Minister Han stepped in as acting president immediately after Yoon was suspended from office late in the evening, in accordance with the Constitution.

Han stressed that every decision that the government makes will be based on the standards of "the Constitution, law and the future of the nation."

Woo echoed Han's sentiment by saying that "the government and the Assembly must work together under one mindset to overcome the current crisis."

The Assembly speaker added that it is their "foremost priority" to "properly handle the current situation and quell the (disruptions) in the state affairs."

The launch of the government-Assembly joint consultative body must be swiftly pursued, Woo highlighted, echoing main opposition leader and Democratic Party Rep. Lee Jae-myung's proposal made during a press conference held around noon.

In the morning, Han and US President Joe Biden reaffirmed the "ironclad" alliance between Seoul and Washington, amid growing uncertainties surrounding the security situation on the peninsula, in a 16-minute phone call, the prime minister's office said.

"Our government plans to carry out diplomatic and security policies without disruptions, as well as make efforts to maintain and develop the South Korea-US alliance without wavering," Han told Biden, according to the prime minister's office.

"It is crucial that we solidify the South Korea-US combined defense posture more than ever, as both (countries) face North Korea's advancing missile threats and a deepening alliance between Moscow and Pyongyang," Han added.

Han reassured Biden that all state affairs would be managed based on the Constitution and the rule of law, emphasizing that no one, including the government, is above the law.

In response, Biden said that the "ironclad" alliance between South Korea and the US remains unchanged, said Han's office. The US president pledged to work closely with South Korea on the strengthening and continued development of the decades-old alliance between the two countries and the cooperation between Seoul, Washington and Tokyo.

Biden also expressed confidence and trust in South Korea's democracy after thanking Han for providing an explanation of the current situation.

South Korea currently faces both domestic and external risks related to Yoon's impeachment. Political turmoil in the country is projected to escalate as the Constitutional Court proceeds with its deliberation on whether to reinstate Yoon to power or formally oust him. The process, which technically kicked-off Saturday evening, could take up to 180 days and if Yoon is removed from office, a snap election will be called.

Several senior defense and military officials have stepped down or been arrested in recent weeks, accused of insurrection or colluding with Yoon in insurrection. This has led to growing concerns over the South's ability to maintain its military deterrence against the North's advancing nuclear and missile threats.