The 94-year-old Buffett also acknowledged his advanced age in his annual letter, telling shareholders he now uses a cane and will spend less time fielding their questions at Berkshire's annual meeting in May.

Warren Buffett started what would become the most profitable investment in his legendary career. Through his company, Berkshire Hathaway Corp. (BRK.A), he began accumulating shares in Apple Inc. (AAPL),

Berkshire Hathaway is committed to its Japanese investments for the long term and has reached an agreement with the companies to own beyond the initial 10% ceiling, Warren Buffett said in his annual letter to shareholders released Saturday.