Online pioneer Marc Andreessen will dial back his role as chief technical officer of America Online to become a part-time strategic adviser, the company announced. Sun Microsystems chief strategist William J. Raduchel will assume the CTO role at AOL, the world's largest online service, the company said. Andreessen will advise AOL on emerging technologies and new investments, splitting his time between working with startups and with AOL on technology issues and potential investments. The move is a shocker -- Andreessen, 27, was named CTO in February following AOL's acquisition of Netscape Communications. Andreessen co-founded Netscape. It was not immediately clear why the change was made. But Andreessen said in a statement he wanted a new role that "will allow me to combine my desire to focus more time on getting involved with startups with the opportunity to contribute to AOL's future success". "Marc will focus on what he likes doing best -- nurturing the rapidly growing number of new companies in Silicon Valley and elsewhere -- while remaining a strategic advisor to AOL on technology and investment issues. His presence in the Valley and his strategic insights will be continuing strengths for AOL," said AOL CEO Steve Case in a statement. AOL's hiring of Raduchel provides further evidence of the growing bonds between the two companies, which are collectively the industry's leading suppliers of Internet services, computer hardware and software. AOL and Sun have worked in close partnership to sell Internet business software since AOL's acquisition of Web pioneer Netscape closed earlier this year. In taking over as AOL's chief technologist, Raduchel will serve as the company's technology strategist, focusing on its network design, technologies and strategic alliances. Raduchel joined Sun in 1988. At various times he held the positions of vice president of finance and chief financial officer, chief information officer, and his last position was chief strategy officer with responsibility for all corporate planning and development. Before Sun, Raduchel was vice president for Document Systems in Xerox's strategic business office. He has also held management positions at Data Resources, McGraw-Hill, the Institute of Defence Analyses and Harvard University. Last month Andreessen filed to sell 940,680 common shares of the Internet services giant, worth $88m (about £55m), according to a Securities and Exchange Commission filing. Reuters contributed to this report.