Silicon Valley legend Steve Jobs, who has been on medical leave for an undisclosed condition since Jan. 17, resigned as chief executive of Apple Wednesday, saying he could “no longer meet my duties and expectations.”

Interim CEO Tim immediately elevated to CEO, while Steve, 55, will stay on as chairman of the board.

“I have always said if there ever came a day when I could no longer meet my duties and expectations as Apple’s CEO, I would be the first to let you know,” Jobs said in a letter to “the Apple community” that was released by the company. “Unfortunately, that day has come.”

While the move was stunning, it was not entirely unexpected.

Steve Jobs had been seen only rarely this year, including at a San Francisco event in March where he unveiled Apple’s iPad 2, the hugely successful follow-on to its hugely successful tablet computer.

“His health clearly wasn’t’ improving and there was going to come a time when he was going to have to set aside,” said Rob Enderle, longtime technology analyst with Enderle Group