South Korean President Park Geun-hye is expected to offer to relinquish some of her power when she addresses the nation on Tuesday but is not expected to announce her immediate resignation, Yonhap news agency quoted a presidential official as saying.

Park's announcement comes as her administration tries to weather an influence-peddling scandal amid growing calls for her to step down.

Yonhap cited a presidential official as saying the address, at 2.30 p.m. (0530 GMT), will not be to announce her resignation.

"It looks like she will indicate a direction to let go (of some power) in the large scheme of things," Yonhap quoted an unidentified official at the presidential Blue House as saying.

Park, whose presidency has been engulfed by the scandal involving a long-time friend, has apologized twice but resisted mounting public calls to quit.

Some lawmakers from Park's own conservative Saenuri party have asked her to resign under an agreement that would allow her to leave office with some dignity, even as opposition parties have stepped up efforts to draw up a motion to impeach her.

A presidential official told Reuters by telephone that the statement would be about the political situation around the favors scandal but did not provide further details. Media reports said she was expected to express her opinion on suggestions that she resign in an orderly manner.

On Saturday, hundreds of thousands of South Koreans rallied for the fifth weekend in a row, calling for Park's resignation. Organizers said the crowd totaled 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 prosecutors' accusations.

Instead of responding to the current investigators' request for questioning, Park, 64, will prepare for an investigation by a special prosecutor that is expected to begin in December, according to her lawyer.

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.