Apple chief executive Steve Jobs is taking medical leave, two years after taking a six-month break when he underwent a liver transplant.

Jobs, a survivor of pancreatic cancer, said chief operating officer Tom Cook would take responsibility for day-to-day operations but he would continue to be chief executive and be involved in major strategic decisions.

"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.

"I have asked Tim Cook to be responsible for all of Apple?s day to day operations. 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," he added.