Former first lady Barbara Bush is in "failing health" and will not seek additional medical treatment, instead focusing on "comfort care", a family spokesman has said.
The 92-year-old wife of George HW Bush has recently had a series of hospital stays.
Spokesman Jim McGrath said the decision had been reached after consulting with her family and doctors. He did not elaborate as to the nature of Mrs Bush's health problems.
Mr McGrath says Mrs Bush is surrounded by "a family she adores" and appreciates the many kind messages and prayers she has been receiving.
"Mrs Bush, now age 92, has decided not to seek additional medical treatment and will instead focus on comfort care," he said.
"It will not surprise those who know her that Barbara Bush has been a rock in the face of her failing health, worrying not for herself - thanks to her abiding faith - but for others."
Mrs Bush is one of only two first ladies who was also the mother of a president. The other was Abigail Adams, wife of John Adams and mother of John Quincy Adams.
She married George HW Bush in 1945. They had six children and have been married longer than any presidential couple in American history.
Mr Bush was in office from 1989 until 1993.
Eight years after she and her husband left the White House, Mrs Bush stood with her husband as their son George W Bush was sworn in as president.