Warren Buffett, the second-richest American, agreed to acquire Fort Worth-based Burlington Northern Santa Fe Corp. for $34 billion, in what would be his largest acquisition ever.

Buffett’s holding company, Berkshire Hathaway Inc., would also assume $10 billion in debt from BNSF, the nation's No. 2 railroad.

Buffett described the transaction as a huge bet on the railroad business and on BNSF chairman, president and chief executive Matthew Rose and his team.

“Most important of all, however, it’s an all-in wager on the economic future of the United States,” said Mr. Buffett. “I love these bets.”

The boards of both companies have approved the transaction. The deal also requires approval by holders of two-thirds of BNSF’s outstanding shares, other than the shares held by Berkshire Hathaway.

It’s also subject to other closing conditions, including review by the U.S. Department of Justice. The deal is expected to close in the first three months of 2010, according to a statement by Berkshire Hathaway and BNSF.