The embattled South Korean president has said she will allow the country’s parliament to decide how long she stays in office and plan for a successor amid calls for her impeachment.

“I will leave to parliament everything about my future including shortening of my term,” she said.

“I will step down from my position according to the law once a way is formed to pass on the administration in a stable manner that will also minimise political unrest and vacuum after ruling and opposition parties’ discussion.”

The main opposition Democratic Party rejected Park’s offer, calling it a ploy to escape being impeached, Yonhap news agency said.

Park Kwang-on, a Democratic Party politician, said it looked like she was trying to delay proceedings.

“She is handing the ball to parliament, when she could simply step down,” he said.

“She is asking the parliament to pick a date for her to resign, which she knows would lead to a discussion on when to hold the presidential election and delay everything.”

OPINION: South Korea’s political morass

Al Jazeera’s Harry Fawcett, reporting from Seoul, said that while Park had stopped short of resigning, her remarks effectively paved the way for her to be replaced.

“She has said she would delegate the opinion of how long her term would last – a potential shortening of her term – to the national assembly. Then she would delegate her political authority to an incoming candidate,” Fawcett said.

“She isn’t officially resigning, but she is giving the national assembly, which has a majority of opposition MPs … the authority this week to decide whether to shorten her presidential term.”

Park had previously rejected calls to resign and dismissed prosecutors’ claims that she colluded with a confidante who allegedly manipulated power from the shadows and extorted companies to amass an illicit fortune.

Her speech came as opposition parties closed in on an impeachment motion against her. They planned to put that motion to the vote on Friday. The country’s two largest opposition parties were also planning on Tuesday to determine a special prosecutor to investigate the scandal independently.

Hundreds of thousands of South Koreans rallied on Saturday for the fifth weekend in a row calling for Park’s resignation. Organisers said the crowd totalled 1.5 million, while the police estimated the crowd at 260,000.

No South Korean president has failed to complete a term since the current democratic system was implemented in 1987. If Park is impeached or resigns, an election would be held in 60 days to nominate a president to serve a five-year term.

Park’s approval rating fell to just 4 percent in a weekly survey released on Friday by Gallup Korea, an all-time low for a democratically elected South Korean president.

Park’s friend, Choi Soon-sil, and a former aide have been indicted in the case. Prosecutors named Park as an accomplice in an investigation into whether big business was inappropriately pressured to contribute money to foundations set up to back Park’s initiatives.

The presidential office and Park’s lawyer have denied the accusations.

Park has acknowledged carelessness in her ties with Choi, who Park has said had helped her through difficult times.

Their friendship dates to an era when Park served as acting first lady after her mother was killed by an assassin’s bullet intended for her father, then-president Park Chung-hee. Five years later, in 1979, Park’s father was murdered by his disgruntled spy chief.