Michael Jackson's father said the King of Pop was not ready perform 50 shows in London, in a TV interview that aired the day the singer was scheduled to start his long-awaited comeback.

Joe Jackson told ABC News that his son told him that he only agreed to perform 10 shows in London, but that the concert promoter booked more shows to bring the total to 50.

I was worried about his health, because all the shows that I'm seeing, no artist can do that many shows back to back like that, Joe Jackson told ABC News in an interview broadcast on Monday. So I knew Michael couldn't do all those shows without some rests in between.

In a statement, Randy Phillips, president and chief executive of concert promoter AEG Live, acknowledged on Monday that the number of shows was originally lower, but said Jackson had agreed to perform more.

Our original agreement with Michael Jackson called for 31 shows, Phillips said.

When the response to the initial announcement of 10 shows was so overwhelming, AEG Live went to Jackson's then advisor, Dr. Tohme Tohme, and asked if the singer would be willing to do more, Phillips said. The first show was scheduled for July 13 with the remainder were spread out until February 2010.

Tohme told AEG Live that Jackson would perform 50, and Jackson himself said he was motivated to embark on a record-setting run of concerts, Phillips said.

The singer, 50, had previously passed a lengthy physical head of his first live concert series in 12 years and was rehearsing in Los Angeles the day before his death.

Jackson died of cardiac arrest on June 25, after he stopped breathing and paramedics were called to his Los Angeles home.

In a separate interview, Michael Jackson's sister, La Toya Jackson, told British newspaper The Daily Mail that her brother was murdered by a conspiracy of people around him.

La Toya Jackson said she believes her brother was overworked to rehearse and prepare for the concert series, and that he was intentionally separated from his family.

After the L.A. Coroner examined Jackson's body, his family ordered a second, private autopsy on the singer.

He had needle marks on his neck and his arms and more about those will emerge in the next few weeks, La Toya Jackson told the Daily Mail.

I cannot discuss that any further as I may jeopardize the investigation, she said. I can, however, say that I have not changed my mind about my feeling that Michael was murdered.

La Toya Jackson also said her suspicions were raised by medical equipment, including oxygen tanks and a stand with a cord hanging down, in a room at her brother's home.

Media reports have said that the dangerous sedative Diprivan -- normally used in hospitals by anesthesiologists -- was found at the singer's home.

Los Angeles police have revealed few details of their investigation, and the L.A. Coroner said it will release the results of its autopsy within weeks.