Biden made the remarks to a few dozen attendees at a Democratic National Committee fundraiser in Rancho Santa Fe, Calif., as he discussed progress in cancer research.

"He asked me to do his eulogy," Biden said, before appearing to catch himself and adding, "excuse me, I shouldn't say that."

"I spent time with Jimmy Carter, and it's finally caught up with him. But they found a way to keep him going for a lot longer than they anticipated, because they found a breakthrough," the president said.

Carter has had multiple health issues over the years, including a bout with cancer. In 2015, he announced that he had been diagnosed with cancer in his liver and brain and soon began radiation. Later that year, he announced he was cancer-free. In 2019, he underwent surgery after a series of bad falls left him with health issues.

Last month, the Carter Center announced that the former president had decided to initiate hospice care at his home in Plains, Ga. "After a series of short hospital stays, former U.S. President Jimmy Carter today decided to spend his remaining time at home with his family and receive hospice care instead of additional medical intervention," the center said.

At 98 years old, Carter is the longest-living American president. He and Biden have known each other since 1976, the White House said. That year, Biden, who was then a senator, became the first elected official outside of Georgia to endorse Carter's run for president.

Carter won that election. He served as the 39th president during the turbulent late 1970s before losing reelection to Ronald Reagan in 1980. In the decades that followed, Carter worked to advance democracy and health initiatives around the world — work for which he was awarded the Nobel Peace Prize in 2002.