Pain Delays Tests on Michael Jackson : Celebrities: New chest discomfort called a ‘temporary setback’ for hospitalized pop star.

Pop superstar Michael Jackson remained hospitalized in stable condition Tuesday after renewed complaints of chest pains prompted his doctor to delay administering scheduled tests.

The 31-year-old Grammy-winning singer was taken to St. John’s Hospital and Health Center in Santa Monica on Sunday evening after experiencing chest discomfort. His doctor said Jackson had a “temporary setback” Monday when he experienced more pain.

On Tuesday, the entertainer rested comfortably in his hospital room while under the observation of his doctor, cardiologist Mark Zatzkis, said Bob Jones, Jackson’s publicist. The singer was expected to begin the testing process late Tuesday or today, Jones said.

Before being hospitalized, Jackson had been rehearsing and following his normal routine of fasting, Jones said.

Jones, who spoke to Jackson briefly Tuesday, said the singer seemed to be in good spirits.

“Mike is a positive person and his spirits are never low,” Jones told reporters outside the hospital.

However, the publicist added that Jackson has experienced a great deal of stress recently. He said the stress stems, in part, from the deaths of his grandmother and entertainer Sammy Davis Jr., a close friend. In addition, Jackson is under pressure to finish an album that is eight months overdue, Jones said.

Jackson began his musical career as the lead singer of the Jackson 5, which produced numerous hits for Motown. The singer eventually went solo and, in 1979, released “Off the Wall,” which sold 12 million copies.

But it was the album “Thriller,” released in 1983, that placed Jackson on the musical map. That work generated numerous Top 10 singles and Grammy awards and became the largest-selling album in the history of recorded music.