Steve Jobs taking medical leave

COO Tim Cook will assume his responsibilities

NEW YORK -- Apple shares tanked after-hours Wednesday on news that CEO Steve Jobs is taking a medical leave of absence until the end of June as his medical condition is "more complex" than originally thought and his health poses a distraction for the company.

In an e-mail to staff published by Apple after the market close, Jobs said he has tapped COO Tim Cook as the executive in charge of day-to-day operations at the tech giant.

"As CEO, I plan to remain involved in major strategic decisions while I am out," Jobs, 53, wrote. "Our board of directors fully supports this plan."

According to Apple's Web site, Cook has been responsible for all of the company's worldwide sales and operations and also heads the Macintosh division. Before Apple, Cook held executive posts at Compaq and IBM, among others.

The Apple leader also serves on the board of Disney and is the entertainment giant's largest individual shareholder. Disney officials weren't immediately available for comment.

Following the Jobs update, Apple's stock fell sharply in after-hours and hit levels below its 52-week low of $79.14. During the regular trading session Wednesday, the stock lost 2.7% to $85.33.

Only last week Jobs said he would continue to fulfill his job functions as CEO despite suffering from a hormone imbalance. He didn't provide specifics on Wednesday as to why his situation is now seen as "more complex."

In his staff memo, Jobs only wrote: "In order to take myself out of the limelight and focus on my health, and to allow everyone at Apple to focus on delivering extraordinary products, I have decided to take a medical leave of absence until the end of June."

Investors have speculated about his health since he lost weight last year, but Jobs has never discussed his condition in full. In 2004, he had announced a successful surgery to treat a rare form of pancreatic cancer.