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.

“I am giving up everything now,” she said in a dramatic, five-minute televised address, offering her third public apology for the scandal that has paralyzed her government for weeks. It was the first time South Koreans had heard from their cloistered leader since a previous televised public apology on Nov. 4.

But opposition lawmakers immediately rejected the offer, calling it a ploy meant to divide her political opponents and allow Ms. Park to survive in office, and they vowed to proceed with impeachment efforts. But their plan to call for an impeachment vote on Friday has been cast into doubt.

Members of Ms. Park’s party who had supported impeachment have now suggested that the vote be delayed until Dec. 9, to give rival parties time to negotiate a date for Ms. Park’s resignation instead. The opposition needs the support of those governing party lawmakers to pass an impeachment bill.