SEOUL, South Korea — President Park Geun-hye of South Korea said Tuesday that she was willing to resign before her term ends, in an effort to head off a pending impeachment vote over a devastating corruption scandal.

She said she would let the National Assembly decide when she should step down to ensure an orderly transfer of power.

Opposition parties had planned to call for a vote Friday in the National Assembly on whether to impeach Ms. Park. Even staunch allies in her own party have appealed to her in recent days to choose an “honorable retreat,” as opposition lawmakers have put it.

“I am giving up everything now,” Ms. Park said in a televised address to the nation, again offering an apology for the corruption scandal that has paralyzed her government for weeks.

“I will leave it to the National Assembly to decide on my resignation, including the shortening of my presidential term,” she said. “If the governing and opposition parties inform me of the way to minimize the confusion and vacuum in state affairs and endure a stable transfer of power, I will step down as president according to their schedule and legal procedures.”

There was no immediate response to Ms. Park’s statement from opposition parties.

Ms. Park’s dramatic gesture Tuesday was also a concession to mounting pressure from ordinary South Koreans, who have taken to the streets in large numbers for five straight Saturdays to demand that she resign or be impeached. Her announcement was an attempt to defuse the political standoff that has been intensifying over a corruption scandal implicating Ms. Park and a longtime friend and secretive adviser, Choi Soon-sil.

Ms. Park’s offer could spare the country several months of political uncertainty that a presidential impeachment would entail. If the National Assembly voted to impeach her, the deeply unpopular Prime Minister Hwang Kyo-ahn, who is not an elected official, would serve as acting president while the Constitutional Court took up to six months to decide whether to ratify the impeachment vote.

Ms. Choi has been charged with extorting the equivalent of tens of millions of dollars from South Korean businesses, and prosecutors have said that Ms. Park helped her to do so. Ms. Park cannot be indicted while in office, but she has been officially identified as a criminal suspect, a first for a president. Ms. Park has also been accused of helping Ms. Choi illegally gain access to confidential government documents.

Ms. Park’s five-year term had been scheduled to end in February 2018.