Apple chief Steve Jobs on Wednesday said he is resigning as CEO of the technology giant he co-founded and named Tim Cook as his successor.

According to his letter "to the Apple Board of Directors and the Apple Community", posted on the Wall Street Journal website, Jobs said, "I hereby resign as CEO of Apple. I would like to serve, if the Board sees fit, as Chairman of the Board, director and Apple employee."

"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. Unfortunately, that day has come." He said he "strongly recommends" that Apple executes its succession plan and names Tim Cook as CEO of Apple.

"I believe Apple's brightest and most innovative days are ahead of it. And I look forward to watching and contributing to its success in a new role. I have made some of the best friends of my life at Apple, and I thank you all for the many years of being able to work alongside you."

A pancreatic cancer survivor, Jobs has been on medical leave for an undisclosed condition since January 17.

Meanwhile, experts opine that Apple might face big test without Jobs in charge. A Wall Street Journal  report said: "Cook isn't the showman that Jobs is, but people who know him call him an operational genius who was responsible for crafting Apple's current supply-chain system and helping to transform the company into one of the most efficient electronics manufacturers today."

Cook is known to be polite, but persistent and unyielding in his demands. He can also absorb a huge amount of data and quickly pinpoint any problems, it added. The journal said Apple's recent revolutionary innovations have also been helped by deputies including Apple Senior Vice-President Jonathan Ive, who oversees the company's industrial design team.

Described as one "sharing a brain with Steve," Ive and his group have been responsible for coming up with the physical look and feel of products that have helped set Apple apart from competitors.

The Journal said other key figures who have been a part of Jobs's inner circle for many years include Scott Forstall, who leads the team responsible for the iPhone's operating system and other software; Eddie Cue, Apple's Vice-President of Internet Services, who is regarded as an "all-purpose fixer"; and Philip Schiller, who runs world-wide marketing.

Analysts also worry that Apple could eventually be lost without Jobs's dominant personality and killer instinct.

"Retention of the current bench may also be difficult because Apple's stock price has surged in recent years, allowing executives to make fortunes from stock options during their careers at the company and giving them less incentive to remain," the WSJ report said.

According to Michael Hawley, a professional pianist and computer scientist who worked for Jobs, Jobs' role at Apple has been more the corporate equivalent of "an unusually gifted and brilliant orchestra conductor". "Steve has done a great job of recruiting a broad and deep talent base," Hawkley said.

The New York Times said Jobs' design decisions were shaped by his understanding of both technology and popular culture. His own study and intuition, not focus groups, were his guide.

"When a reporter asked what market research went into the iPad, Jobs had replied, "None. It's not the consumers' job to know what they want," the Times report added.