Yoon had until Thursday defied requests by the court to submit documents as well as summons by investigators in a separate criminal case over his martial law declaration on Dec. 3, drawing criticism even from some members of his party.

Two lawyers in Yoon's legal team are set to attend the court hearing, one a former prosecutor and the other a former spokesman for the Constitutional Court, according to a message to reporters from Seok Dong-hyeon, a lawyer advising Yoon. The two could not be immediately reached for comment.

The unexpected martial law decree and swift political fallout shocked the nation and financial markets, unsettling key allies the United States and Europe which had seen Yoon as a staunch partner in global efforts to counter China, Russia, and North Korea.

The crisis intensified this week as the opposition Democratic Party vowed to impeach Prime Minister Han Duck-soo who is serving as acting president after he rejected a call to immediately appoint three justices to the Constitutional Court to fill vacancies.

Parliament is scheduled to meet on Friday afternoon. The Democratic Party has said it would bring to a vote a motion to impeach Han.

The party has clashed with the Yoon-appointed prime minister over the justices, as well as bills calling for special prosecutors to investigate the president.

On Thursday, Han said it was beyond his remit as a caretaker president to appoint the justices without bipartisan agreement.

The vote to determine Han's fate comes around the time the Constitutional Court holds its first hearing in a case that will decide whether Yoon is reinstated or permanently removed from office.

The court has 180 days to decide whether to reinstate Yoon or remove him. In the latter scenario, a new presidential election would be held within 60 days.

Yoon is not required to attend the hearing.