"At my request, the board of directors has granted me a medical leave of absence so I can focus on my health. I will continue as CEO and be involved in major strategic decisions for the company," Jobs said in an email to Apple employees.
Jobs said he had asked Tim Cook "to be responsible for all of Apple's day to day operations" in his absence.
"I have great confidence that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011.
"I love Apple so much and hope to be back as soon as I can. In the meantime, my family and I would deeply appreciate respect for our privacy."
Jobs went on a medical leave in 2009, and later disclosed he had underwent a liver transplant as part of treatment for pancreatic cancer.
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