Main opposition Democratic Party (DP) floor leader Park Chan-dae has warned that his party will make an "important decision" if acting President Han Duck-soo fails to appoint a ninth Constitutional Court justice by Tuesday.

Park issued the warning on Sunday at the National Assembly, stating that the DP would take action if Han does not fulfill his constitutional duty by the deadline.

The floor leader argued that sufficient time has passed to conclude that the trust of the people, who expect the acting president to faithfully perform his duties in accordance with the Constitution and the law, has been betrayed.

Park emphasized that the National Assembly, as a constitutional institution, has a duty to safeguard the constitutional order, and the DP will exercise all powers granted to it.

A group of the DP's first-term lawmakers announced at a news conference on Friday that they would seek Han's impeachment again unless he appoints the ninth Constitutional Court justice, Ma Eun-hyuk, by Sunday.

The DP lawmakers also issued similar warnings for other ministers, vowing to impeach them immediately if they succeed Han and fail to make the appointment.