It's a milestone Warren Buffett probably wishes he weren't approaching.

Berkshire Hathaway, the conglomerate he's run for more than five decades, reported Friday that it held just shy of $US100 billion ($126 billion) in cash at the end of the second quarter.

While that figure highlights the staggering money-making ability of the businesses he's collected over the years, it's also a burden. Because Berkshire doesn't pay a dividend and rarely buys back its own stock, Buffett is on the hook to find ways to invest those funds.

"To put that money to work would be great," said David Rolfe, chief investment officer at Wedgewood Partners, a money manager overseeing about $US6 billion including Berkshire stock. But the "list of companies that he would like to own is very, very small."