Buffett remains in good health and has no plans to retire, but he says Berkshire's board regularly discusses succession and knows who it would pick as CEO if the need arises.

Buffett's assistant Carrie Kizer said he was travelling Monday and would not be immediately available to comment.

The revelation about a fourth candidate reinforces speculation that Burlington Northern Santa Fe CEO Matt Rose became a contender after Berkshire acquired the railroad last year.

The other Berkshire managers believed to be on the short list are David Sokol, chairman of NetJets and MidAmerican Energy; Ajit Jain, who runs Berkshire's reinsurance division; Greg Abel, president and CEO of MidAmerican Energy; and Tony Nicely, chief executive of Geico.

Berkshire shareholder Glenn Tongue, who is a managing partner at the T2Partners investment firm, said he's satisfied with the company's succession planning and the details Buffett has disclosed. He said naming the CEO candidates could actually be counter-productive because executives who were left off the list might be discouraged.

"I think he's walked the line on succession planning exactly appropriately," Tongue said.

Buffett says his primary responsibilities at Berkshire are deciding how best to invest the company's cash and keeping key managers of Berkshire subsidiaries happy. Buffett consults with 87-year-old Vice Chairman Charlie Munger on all major decisions.

But Buffett and Munger employ a remarkably hands-off approach to managing Berkshire's roughly 80 subsidiaries. Berkshire's insurance, furniture, utility, jewelry, clothing, carpet and other companies largely operate independently of Berkshire's 21-person headquarters.

On the investment side, Buffett has said Berkshire's investment duties would likely be split among three or more different managers who would report to the next CEO. Those investment managers will be in charge of Berkshire's stock portfolio and its other investments.

Buffett has said his company's board had a list of several internal and external investment managers who could manage Berkshire's investments. Last fall, Buffett hired Todd Combs to manage $1 billion to $3 billion of Berkshire's $158 billion investment portfolio, but no other candidates for the investment manager jobs have been named.

Buffett has recommended that his son Howard take over as chairman to ensure Berkshire's culture is preserved, but that decision will be made by Berkshire's board. Howard Buffett already serves on the board.