Apple Inc CEO Tim Cook walked onstage to kick off a Tuesday event at which the fifth version of the company's iPhone is expected to be unveiled.

Cook, an operations and supply-chain expert not known for pitching products, will preside over the new smartphone's launch at Apple's headquarters in Silicon Valley, standing in for co-founder Steve Jobs in his new role as chief executive.

Jobs, a pancreatic cancer survivor who stepped down as CEO in August after taking his third medical leave, had not yet appeared on stage.

(Reporting by Poornima Gupta and Alexei Oreskovic; Editing by Phil Berlowitz)