SEOUL -- South Korea's main liberal opposition Democratic Party said on Thursday that it will vote on a motion to impeach Prime Minister Han Duck-soo on Friday.

Park Chan-dae, the party's floor leader, said in a statement that his party had submitted the impeachment motion against Han and reported it to the National Assembly's plenary session.

Han became an acting president following President Yoon Suk-yeol's impeachment over his martial law declaration on the night of Dec. 3 which was revoked by the National Assembly hours later.

Yoon was impeached by the National Assembly on Dec. 14. Since then, the constitutional court would deliberate it for up to 180 days, during which Yoon's presidential power is suspended.

Han said in a televised address earlier in the day that he will delay the appointment of constitutional court justices until the ruling and opposition parties reach an agreement.

The Democratic Party floor leader called Han's address as an official refusal to approve the appointment contributing to insurrection, over which investigative agencies looked into the impeached president.

Park Sung-joon, the party's deputy floor leader, told reporters that the Democratic Party will vote on the motion to impeach the prime minister during a plenary session on Friday.

The voting process was underway in the National Assembly to appoint three constitutional court justice nominees, who are required to be approved by an acting president.