Billionaire investor Warren Buffett will step down as chairman of Berkshire Hathaway, the conglomerate announced on Friday. The news brings to an end the revered investor's more than half-a-century of running the group, which he turned into a financial behemoth. Buffett's resignation is "effective immediately" and he will remain a member of the board of directors, Berkshire Hathaway said in a statement. Buffett's son Howard Buffett will take over as chairman, the statement added. The 96-year-old had announced plans last year to retire from leading the business group. Berkshire Hathaway, a former small textile company, has grown over the years into a gigantic conglomerate under Buffett's leadership, and is now worth over US$1 trillion on Wall Street -- a first for an American group outside the tech sector. Today, his conglomerate owns dozens of businesses, from Duracell batteries to US insurer Geico, and shares in carefully selected companies, from Coca-Cola to Bank of America. (AFP) Edited by Robert Kemp