Speaking at Berkshire's annual shareholder meeting in Omaha, Nebraska, Buffett also said he would consider raising the threshold "a little" if he found Berkshire with so much money that it "burns a hole in your pocket."

He said that could happen if Berkshire's cash hoard rose to $100 billion or $120 billion, a level it has never reached and perhaps double what it is now, following January's $32-billion purchase of industrial parts maker Precision Castparts Corp.

"The stock is worth significantly more than 1.2" times book value, he said.

Berkshire is expected to disclose its book value per share when it releases final first-quarter results on May 6.

(Reporting by Jonathan Stempel in New York; Editing by Nick Zieminski)

Stocks treated in this article : Berkshire Hathaway Inc., PRECISION