On Sunday, South Korea's acting president, Han Duck-soo, sought to reassure the nation's allies and ease concerns in the financial markets after President Yoon Suk Yeol was impeached and suspended from office the day before over an attempt to impose martial law.

Han spoke with US President Joe Biden over the phone, according to statements from both the White House and Han's office.

In a statement from his office, Han said that "South Korea will carry out its foreign and security policies without disruption and strive to ensure the South Korea-US alliance is maintained and developed steadfastly."

To further stabilize the country's leadership, the main opposition party announced it would not pursue impeachment of Han over his role in Yoon's December 3 martial law decision.

"Given that the prime minister has already been confirmed as acting president and considering that excessive impeachments could lead to confusion in national governance, we have decided not to proceed with impeachment procedures," Democratic Party leader Lee Jae-Myung told reporters.

Han, a seasoned technocrat chosen by Yoon as prime minister, was appointed acting president in line with the constitution while Yoon's case was reviewed by the Constitutional Court.

'US-South Korea alliance remains'

Yoon's unexpected declaration of martial law and the resulting political crisis unsettled markets, while South Korea's diplomatic partners expressed concerns about the country's ability to counter the Democratic People's Republic of Korea (DPRK). 

According to Han's office, Biden assured Han that the US-South Korea alliance remained steadfast, emphasizing that Washington would continue to collaborate with Seoul to strengthen the alliance and enhance trilateral cooperation, including with neighboring Japan.

In a statement, the White House said that the US president "expressed his appreciation for the resiliency of democracy and the rule of law in the ROK and reaffirmed the ironclad commitment of the United States to the people of the ROK," using the abbreviation for the country's formal name, the Republic of Korea.

"President Biden expressed his confidence that the Alliance will remain the linchpin for peace and prosperity in the Indo-Pacific region during Acting President Han’s tenure."

Han convened his cabinet and National Security Council shortly after Saturday's impeachment vote and vowed to maintain military readiness to prevent any breach of national security.

The Constitutional Court has up to six months to decide whether to remove or reinstate Yoon. If he is removed or resigns, new elections will be held within 60 days.

'Market control after impeachment' 

South Korean shares rose for a fourth consecutive session on Friday, driven by optimism that political uncertainty would ease following the impeachment vote in parliament, which came after a failed vote the previous week.

Democratic Party leader Lee highlighted the urgent issue of declining consumption due to insufficient domestic demand and the government's reduced fiscal role. He proposed creating a National Stability Council for Governance, composed of the government and parliament, to address finance, the economy, and public welfare.

Lee also called for a supplementary budget, which could include support for small businesses and investments in artificial intelligence and infrastructure to prevent energy shortages.

Parliament, controlled by Lee's party, passed a 673.3 trillion won ($470.6 billion) 2025 budget bill on Tuesday, cutting the government's original proposal of 677.4 trillion won. However, no agreement was reached with Yoon's People Power Party or the government.