Warren Buffett's Berkshire Hathaway Inc said it agreed to buy railroad Burlington Northern Santa Fe Corp in Buffett's biggest acquisition ever.

In a statement, Buffett said railroads are key for the United States' future growth, and will only grow when the nation grows.

...(I)t's an all-in wager on the economic future of the United States, Buffett said. I love these bets.

Berkshire Hathaway would pay $100 a share for the railroad in cash and stock for the 77.4 percent of its shares that it does not already own. The deal values Burlington Northern at $34 billion.

(Reporting by Helen Chernikoff, editing by Gerald E. McCormick)