Cash has been in hospital several times recently

The singer, 71, was due to attend the MTV Video Music Awards in New York, where his song Hurt won best cinematography.

The country star was being held for observation, said a spokeswoman for the Nashville Baptist Hospital.

Cash has recently been admitted to hospital several times.

Six nominations

Cash's manager, Lou Robin, said the stomach problem was an "isolated incident" and that Cash planned to travel to Los Angeles next week to begin work on a new album if he was better.

Cash was nominated in six MTV Video Music Awards categories for the track Hurt, a cover of a song by hard rock band Nine Inch Nails. Mr Robin said on Thursday that Cash would watch the MTV ceremony on TV in hospital.

The video for Hurt has been critically acclaimed

The country star's wife, singer June Carter-Cash, died in May after complications from heart surgery.

Cash, who became a star in the 1950s and 60s with songs such as Ring of Fire, I Walk the Line and A Boy Named Sue.

Despite ill-health over the last decade, Cash became an icon to a new generation of music fans with a series of albums that included covers of songs by artists such as U2, Nick Cave, Tom Waits and Will Oldham.

The critically-acclaimed video for Hurt was directed by Mark Romanek, who was the director of the Robin Williams thriller One Hour Photo.