NEW YORK (CNNMoney)Investor Warren Buffett said his biggest worry about the Federal Reserve’s policy of buying assets is how the markets will react once the central bank starts selling its holdings.

In an appearance on CNBC Monday, the chairman of Berkshire Hathaway (BRKA, Fortune 500) pointed to the sell-off in stocks a couple of weeks ago after the Fed’s minutes suggested some members supported slowing asset purchases from their current pace. He said that was just a small preview of what could be extreme market reaction once the Fed actually does start selling the trillions in Treasuries and mortgages it now holds. The Fed is buying $45 billion of Treasuries and $40 billion of mortgages each month through a policy known as quantitative easing.  Read more