Yoon's move to impose military rule on Dec. 3 was rescinded before six hours but it plunged the country into a constitutional crisis and widespread calls for him to step down for breaking the law.
Yoon on Thursday vowed to "fight to the end," blaming the opposition party for paralysing the government and claiming a North Korean hack into the election commission made his party's crushing defeat in an April parliamentary election questionable.
Democratic Party leader Lee called Yoon's remarks "a declaration of war" against the people. "It proved that impeachment is the fastest and the most effect way to end the confusion," he said.
Yoon survived the first attempt to impeach him last Saturday when most of his ruling People Power Party (PPP) boycotted the vote. Since then some PPP members have publicly supported a vote to impeach him.
Opposition parties, which control the single-chamber parliament, have introduced another impeachment bill and plan to hold a vote on Saturday. They need at least eight PPP members to join to pass the bill with the two-third majority required.
