The main opposition Democratic Party on Thursday was poised to push for the passage of a bill mandating a special counsel investigation into the military's response to a Marine's death amid fierce protest from the ruling party.

The ruling People Power Party has been staging a filibuster since Wednesday afternoon to block the passage of the bill after it was tabled during the National Assembly's plenary session.

The special probe bill calls for a special counsel to look into allegations that the presidential office and the defense ministry inappropriately interfered in the Marines' investigation into the death of Cpl. Chae Su-geun, killed during a search mission for victims of heavy downpours in July 2023.

The DP-led bill had initially passed through the previous National Assembly but was scrapped in a revote after President Yoon Suk Yeol vetoed it. The DP proposed it again after the new National Assembly came into office in late May.

DP floor leader Park Chan-dae warned Yoon against vetoing the bill.

"He should bear in mind that if he exercises veto rights, he will be put on a path to catastrophe and downfall," Park said during a party policy meeting.

The Assembly is expected to put the bill to a vote after the PPP's filibuster ends Thursday afternoon.

Under the National Assembly Act, a filibuster can be stopped after 24 hours if at least three-fifths of all parliament members, or 180 lawmakers, consent to it.

Immediately after the bill was tabled the previous day, DP lawmakers submitted a request for an end to the filibuster. (Yonhap)