IBM's long-serving chief executive, Sam Palmisano, will step down as CEO on January 1 2012 and be replaced by global sales head Virginia Rometty.

International Business Machines Corp said on Tuesday that Palmisano, credited with helping transform the once PC-focused company into a services company during a near-decade-long run starting in 2002, will stay on as chairman.

Ginni Rometty, 54, oversees 170 global markets for Big Blue and is responsible for IBM's worldwide results.