GREENWICH, Conn. — Genesee & Wyoming said it will buy RailAmerica for about $1.39 billion, combining the two largest short-line and regional rail operators in North America.

The combined company will operate 108 railroads in the United States and abroad. The deal will diversify what the railroads carry, offering protection from prolonged weakness in certain shipments like coal. Genesee & Wyoming also operates in Australia, the Netherlands, and Belgium.

Genesee & Wyoming will pay $27.50 in cash for each share of RailAmerica Inc., of Jacksonville, Fla. The price represents a premium of nearly 11 percent over RailAmerica’s price of $24.81 on Friday.

RailAmerica has been shopping around for a possible buyer since May. The deal will expand Genesee’s network to 37 US states from 24.