Blues legend Etta James is in a stable condition after suffering complications during abdominal surgery in Los Angeles, her manager has confirmed.
Etta James is best known for her ballad At Last
The singer, 69, has been in hospital since the operation in mid-June.
She was due to tour with BB King and Al Green this summer, but will not be able to make any dates before late August.
"If it had been left solely up to her, she would have checked herself out of the hospital and started the tour regardless," the star's manager said.
"However, her doctor advised that were she to do so, it would put her at very great risk."
Her slot on the tour is being filled by R&B singer Chaka Khan until further notice.
Discovered by legendary band leader Johnny Otis, James' career has spanned five decades.
Throughout the 1950s, she was a mainstay of Otis' R&B revue, and scored hits with songs like The Wallflower (Dance With Me, Henry) and Good Rockin' Daddy.
She diversified into mainstream blues during the 1960s, after signing with Chess Records - and is perhaps best known for her 1961 ballad At Last.
The singer developed a heroin addiction in the 1960s that was to last for more than a decade, and saw her spend time in psychiatric hospital.
After kicking her drug habit, she remained a popular concert performer - although further chart success largely eluded her.
She was inducted into the US Rock and Roll Hall of Fame in 1993, and won the first of three Grammy awards for 1994's Mystery Lady: The Songs of Billie Holiday.
A year later, she scored a top ten hit in the UK when her version of I Just Wanna Make Love To You was featured in an advertisement for Coca-Cola.