The billionaire investor's Berkshire Hathaway holding group said it would purchase the 77.4 percent of Burlington Northern Santa Fe (BNSF) that it does not currently own for US$100 per share in cash and stock.

The offer values the rail operator at US$44 billion, including US$10 billion in debt. Buffett will invest some US$26.3 billion for the new stake.

"It's an all-in wager on the economic future of the United States. I love these bets," said Buffett, known in financial circles as the "Oracle of Omaha" for his investing acumen.

The takeover bid represents a 31 percent premium over BNSF's closing share price Monday.

"Our country's future prosperity depends on its having an efficient and well-maintained rail system," said Buffett, Berkshire Hathaway's chairman and chief executive, adding that the deal was the biggest ever for his storied investment fund.

"America must grow and prosper for railroads to do well," Buffett said, adding that "the investment in BNSF is a huge bet on that company... and the railroad industry."

Burlington Northern president, chairman and CEO Matthew Rose said the company welcomed deal.

"We are thrilled to have the opportunity to become a part of the Berkshire Hathaway family," said Rose.

"This transaction offers compelling value to our shareholders and is in the best interests of all of our constituents including our customers and employees."

The deal requires approval by holders of two-thirds of the railway's shares not already held by Berkshire Hathaway and review by regulators.

The transaction is expected to be completed in the first quarter of next year.