Albertina Walker, hailed as the "Queen of Gospel", died Friday at age 81.

The Grammy-winning singer, who was committed to the preservation of gospel music, died of respiratory failure at RML Specialty Hospital in Chicago, as reported by The Associated Press.

Walker began singing in the children's choir of West Point Baptist Church in Chicago at age four. At 22, she organised The Caravans, which became a world famous gospel singing group. They recorded such hits as "Mary Don't You Weep", "Sweeping Through the City", "Walk Around Heaven", and "Lord Keep Me Day by Day".

During her time with the group, she also discovered and launched the careers of Inez Andrews, Shirley Caesar, Cassietta George, Dorothy Norwood and Delores Washington, among others.

She later launched a successful career as a solo artist.

Walker has written over 100 songs and recorded 71 albums. Her music has been recorded and emulated by such artists as Aretha Franklin, Ray Charles and Al Green.

She has sung for several US presidents including Barack Obama, George W Bush and Bill Clinton.

Obama said he was saddened by her passing and called her an "American icon".

In 2001, she was inducted into the Gospel Music Hall of Fame along with the late Elvis Presley, Kurt Kaiser, Keith Green, Larry Norman, Doris Akers, Wendy Bagwell & the Sunliters and The Rambos. The following year, she was honoured by Bush for her contributions to gospel music.

In 2006, she reunited with The Caravans and released an album entitled Paved The Way. According to her website, the group was also working on a 2010 release.

A public viewing for Walker is scheduled for October 14 at West Point Baptist Church. The viewing will be followed by a Celebration of Life Worship Service the following day.