Veteran actress Betty White, best known for her role in The Golden Girls and whose career spanned eight decades, has died aged 99.

Less than three weeks before her 100th birthday, the actress reportedly died at her home on Friday.

Her agent and close friend Jeff Witjas told People magazine: “Even though Betty was about to be 100, I thought she would live forever.”

She had a career spanning 80 years and had Emmy-winning roles on television sitcoms The Golden Girls and The Mary Tyler Moore Show.

White was still starring in a TV sitcom, Hot in Cleveland, at age 92 until it was cancelled in late 2014.

“Old age hasn’t diminished her,” the New York Times wrote in 2013. “It has given her a second wind.”

US president Joe Biden is among those to have paid tribute, telling reporters: “That’s a shame. She was a lovely lady.”

First Lady Jill Biden added: “Who didn’t love Betty White? We’re so sad.”

Hollywood comedy actor Ryan Reynolds tweeted to say White was “great at defying expectation”.

He continued: “She managed to grow very old and somehow, not old enough. We’ll miss you, Betty. Now you know the secret.”

White said her long career was a result of good health, good fortune and loving her work.

“It’s incredible that I’m still in this business and that you are still putting up with me,” White said in an appearance at the 2018 Emmy Awards ceremony, where she was honoured for her long career.

White was not afraid to mock herself and throw out a joke about her sex life or a snarky crack that one would not expect from a sweet-smiling, white-haired elderly woman.

She was frequently asked if, after such a long career, there was anything she still wanted to do.

Her standard response was: “Robert Redford.”

White, who was born in Oak Park, Illinois, in 1922, started her entertainment career in radio in the late 1930s.

She made her TV debut singing on an experimental channel in Los Angeles in 1939.

After serving in the American Women’s Voluntary Service, which helped the US effort during World War Two, she was a regular on Hollywood on Television, a daily five-hour live variety show, in 1949.

A few years later she became a pioneering woman in television by co-founding a production company and serving as a co-creator, producer and star of the 1950s sitcom “Life With Elizabeth”.

Through the 1960s and early 1970s White was seen regularly on television, hosting coverage of the annual Tournament of Rose Parade and appearing on game shows such as “Match Game” and “Password”.

White reached a new level of success on “The Mary Tyler Moore Show,” playing the host of a home-making television show, the snide, lusty Sue Ann Nivens, whose credo was “a woman who does a good job in the kitchen is sure to reap her rewards in other parts of the house”.

White won best-supporting actress Emmys for the role in 1975 and 1976.

She won another Emmy in 1986 for The Golden Girls”, a sitcom about four older women living together in Miami that featured an age demographic rarely highlighted on American television.

White also was nominated for an Emmy six other times for her portrayal of the widowed Rose Nylund, a sweet, naive and ditzy Midwesterner, on the show, which ran from 1985 to 1992 and was one of the top-rated series of its time.

After a less successful sequel to “The Golden Girls” came a series of small movie parts, talk-show appearances and one-off television roles, including one that won her an Emmy for a guest appearance on “The John Larroquette Show.”

By 2009 she was becoming ubiquitous with more frequent television appearances and a role in the Sandra Bullock film “The Proposal”.

In 2010, she appeared as the slightly unhinged professor June Bauer in the popular US sitcom Community.

White also worked for animal causes.

She once turned down a role in the Hollywood movie “As Good as It Gets” because of a scene in which a dog was thrown in a garbage chute.

White had no children and her third and final husband of 20 years, Allen Ludden, died in 1983.