SEOUL, South Korea (AP) — South Korea’s main opposition party said Tuesday it will seek to impeach acting leader Han Duck-soo after he missed an opposition-set deadline to approve independent investigations into impeached President Yoon Suk Yeol and his wife.

If realized, Han’s impeachment would further deepen South Korea’s political tumult and worries by neighboring countries caused by Yoon’s stunning Dec. 3 martial law declaration and ensuing impeachment. Han, the country’s No. 2 official, has taken over presidential powers and duties since Yoon’s impeachment. If he's impeached too, the finance minister is next in line.

The main liberal opposition Democratic Party, which holds a majority in parliament, has slammed Han for vetoing several opposition-sponsored bills, including a controversial agriculture bill. It also urged Han to quickly appoint justices to vacant seats on the Constitutional Court, which is reviewing Yoon's impeachment and will determine whether to dismiss or reinstate him.

Filling the court's three empty posts could make conviction more likely, as it requires the support of six of the court's nine possible members.

The Democratic Party also demanded that Han approve by Tuesday bills calling for the appointments of special prosecutors to investigate Yoon for rebellion over his marital law decree, and his wife for corruption and other allegations.

But Han didn’t do so during Tuesday’s Cabinet Council meeting, calling for the ruling and opposition parties to negotiate.

Democratic Party floor leader Park Chan-dae responded that there's no room for negotiations about a Yoon investigation, and that his party would begin steps toward an impeachment at once.

“We’ve clearly warned that it’s totally up to Prime Minister Han Duck-soo whether he would go down in history as a disgraceful figure as a puppet of rebellion plot leader Yoon Suk Yeol or a public servant that has faithfully carried out the orders by the public,” Park told a televised party meeting.

Korean prosecutors and other officials are separately probing whether Yoon committed rebellion and abuse of power, but he’s ignored requests by investigative agencies to appear for questioning and allow searches of his office.

Yoon’s defense minister, police chief and several other senior military commanders have already been arrested over the deployment of troops and police officers to the National Assembly, which prompted a dramatic standoff that ended when lawmakers managed to enter the chamber and voted unanimously to overrule Yoon's decree.

The governing People Power Party said that the opposition's impeachment threats are interfering with Han’s “legitimate exercise of authority." Floor leader Kweon Seong-dong, a Yoon loyalist, said the Democratic Party’s “politics of intimidation have reached their peak.”

An impeachment vote would face legal ambiguities. Most Korean officials can be impeached with a simple majority of parliament, but impeaching the presidents takes two-thirds. The rival parties differ on which standard would apply to an acting president.

The Democratic Party controls 170 of the National Assembly's 300 seats, so it would need support from members of other parties including Yoon's own to get a two-thirds majority.

The Constitutional Court has up to six months to determine Yoon's fate. If he's thrown of office, a national election to find his successor must take place within two months.