SEOUL — South Korea’s ruling party has thrown its support behind attempts to impeach embattled President Yoon Suk Yeol over his ill-fated decision to declare martial law that sparked a political crisis and widespread public anger in the country.

The announcement came moments before Yoon delivered a defiant speech Thursday in which he attempted to justify his hugely controversial martial law decision and rejected growing calls from across the political spectrum for him to stand down.

The People Power Party (PPP) had initially refused to back impeachment, hoping instead Yoon would resign from office. But its leadership said attempts to persuade him had made no progress.

“We tried to find a better way than impeachment, but that other way is invalid,” party leader Han Dong-hoon said. “Suspending the president from his duties through impeachment is the only way for now, to defend democracy and the republic.”

The main opposition Democratic Party is preparing a new impeachment motion against Yoon, with a vote expected as soon as Saturday. The president survived an impeachment bid last weekend when PPP members boycotted the vote.

But after his party threw its weight behind impeachment, Han said PPP lawmakers were now free to vote according to their “belief and conscience.”

“I believe our party members will vote for the country and the people,” he said.

The PPP’s reversal Thursday dramatically increases the pressure on Yoon and the likelihood that the next impeachment attempt will be successful.

Yoon has faced mounting calls to stand down since he declared a military emergency on December 3, accusing the main opposition party of “anti-state activities,” sympathizing with North Korea and blocking legislation and budgets.

The surprise late night announcement, which was blocked by lawmakers within hours, was met with shock and anger across the country, which remains deeply scarred by the brutality of martial law imposed during decades of military dictatorship before it won a long, bloody fight for democracy in the 1980s.

Dramatic scenes from that night showed security forces breaking through windows in the National Assembly to try and prevent lawmakers from gathering, and protesters confronting riot police.

In the days since, pressure on Yoon has grown, with protesters and opposition figures demanding his impeachment – and support wavering even within his own party and the military.

Police have launched an investigation into Yoon and other top officials on treason allegations. And on Tuesday, lawmakers approved a special counsel to investigate whether Yoon committed insurrection and abused his power by issuing martial law. Yoon has also been barred from leaving the country.

The following day, South Korean police raided the presidential office, a presidential security official confirmed to CNN.

Last week, South Korean prosecutors detained former defense minister Kim Yong-hyun, who allegedly recommended the martial law imposition and resigned in the wake of the scandal. Kim attempted to end his own life in custody late Tuesday, according to the head of the country’s correctional service.

In South Korea’s increasingly partisan political environment, Yoon has portrayed the opposition, led by the Democratic Party, of being overly soft on North Korea, which they deny.

In his speech Thursday, Yoon portrayed his brief declaration of martial law as an attempt to break the political stalemate, while accusing the opposition of “siding with North Korea, scratching the government that is struggling to respond” to Pyongyang’s launches of trash balloons into the South, illegal nuclear armament and missile threats.

“I don’t know which country the party belongs to and which country the National Assembly belongs to,” Yoon said.

A former prosecutor and conservative firebrand, Yoon has had a difficult two years in office. He has faced plummeting approval ratings over economic issues and a series of scandals involving his wife and political appointments that prompted calls for him to resign.

And in recent months, gridlock in parliament had left him a lame-duck president prevented from moving forward on legislation to cut taxes and ease business regulations, as his main rivals in the Democratic Party used the legislature to impeach key cabinet members and hold up a budget bill.

Even as his hold on the country has become more and more tenuous, Yoon has remained defiant.

“I will fight until the last moment with the people,” Yoon said in his speech Thursday.

“I apologize again to the people who might have been surprised and nervous due to the short-lived martial law. Please trust in my passionate loyalty for you, the people.” — CNN