BARBARA Bush, wife of the 41st US President George HW Bush and mother of the 43rd US President George W Bush, has died at home in Houston. She was 92.

A statement from the Office of George H.W. Bush described her as a "relentless proponent of family literacy" in confirming the death.

Her death came after an April 15 statement from her husband's office, which revealed she was in "failing health" and had "decided not to seek additional medical treatment", preferring to "focus on comfort care".

As first lady from 1989 until the start of 1993, Barbara Bush was a popular national figure known for her sometimes blunt talk and self-deprecating wit. She once said that she let her hair go white because dyed hair didn't look good on her, and admitted to wearing a string of pearls to hide the wrinkles in her neck.

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.

Barbara Bush (nee Pierce) first met George H.W. Bush when she was 17 years old and they married in January 1945, when she was 19. They had six children and have been married longer than any presidential couple in American history.

Eight years after she and her husband left the White House, Mrs Bush stood with her husband as their eldest son was sworn in as president.

In a statement George W. Bush wrote that his family was "sad, but our souls are settled because we know hers was.

"Barbara Bush was a fabulous First Lady and a woman unlike any other who brought levity, love and literacy to millions. To us she was much more. Mom kept us on our toes and laughing until the end. I'm a lucky man that Barbara Bush was my mother. Our family will miss her dearly and we thank you all for your prayers and good wishes."

Mrs Bush's second son, Jeb, also pursued a career in politics. He was the first two-term Republican governor of the state of Florida and was an unsuccessful contender for the GOP's nomination for the presidency in 2016, losing to Donald Trump.

In a statement posted on Facebook Jeb Bush wrote: "Columba and I join every member of the Bush family in offering our sincere gratitude for the outpouring of love and support for my Mom in recent days, and throughout her remarkable life. I'm exceptionally privileged to be the son of George Bush and the exceptionally gracious, gregarious, fun, funny, loving, tough, smart, graceful woman who was the force of nature known as Barbara Bush. Thank you for your prayers, and we look forward to celebrating and honoring her life and contributions to our family and great nation in the coming days."

Canadian Prime Minister Justin Trudeau tweeted: "Always a friend to Canada, Barbara Bush leaves a legacy of dignity, grace, service and devotion to family. Sophie and I send our deepest condolences to Presidents George H.W. and George W. Bush, their family, and to all Americans."

Conservative broadcaster Bill O'Reilly added: "Barbara Bush matriarch of a great, patriotic family, dies at 92. Historical women."

Fellow TV commentator Larry King tweeted: "Our dear Barbara Bush. A grand lady, a great friend...she made the White House a brighter place. How we will miss you! Rest In Peace"

BARBARA BUSH'S LEGACY

Her major legacy was The Barbara Bush Foundation for Family Literacy, which she began during her White House years.

The foundation aimed to improve the lives of disadvantaged Americans by boosting literacy among parents and their children and has awarded more than $40 million to create or expand more than 1500 literacy programs nationwide.

"Focusing on the family is the best place to start to make this country more literate, and I still feel that being more literate will help us solve so many of the other problems facing our society," she wrote in her 1994 memoir.

George W. Bush noted in his post-presidency book, Decision Points, that he inherited a quick, blunt temper from his mother. His wife, Laura, said her mother-in-law "managed to insult nearly all of my friends with one or another perfectly timed acerbic comment."

Barbara Bush kept her sarcasm under wraps in public, though one noted slip came in 1984 when her husband was running for re-election as vice president with President Ronald Reagan. Their Democratic challengers, Walter Mondale and Geraldine Ferraro, questioned whether wealthy people like the Bushes could relate to average Americans. An irritated Barbara Bush told a reporter that Ferraro was a "$4 million - I can't say it - but it rhymes with rich." Bush later said she meant "witch" and apologised; Ferraro accepted the apology.

Bush's trademark wit was demonstrated again after she wore a triple-strand false pearl necklace to her husband's inauguration in 1989.

Bush later said she selected them to hide the wrinkles in her neck. The candid admission only bolstered her common sense and down-to-earth public image. A version of the necklace, "the famous triple strand, hand-knotted on a gold-toned clasp," was even available for $125 at the George Bush Presidential Library and Museum at Texas A&M University.

Another long recognised facet of her public image was her snowy white hair.

Her brown hair began to gray in the 1950s while her 3-year-old daughter, Pauline, known to her family as Robin, underwent treatment for leukaemia. She died in October 1953. Barbara Bush eschewed dying her hair, which ultimately turned white. She later said that dyed hair didn't look good on her and credited the colour to the public's perception of her as "everybody's grandmother."

Her son George said that a "crowning achievement" of his father, who was fond of coming up with nicknames for friends and family, was anointing Barbara, "The Silver Fox."