U.S. trucking feeling pressure from greener trains

* Congress could give tax break for freight rail expansion

* Trucks use three times more energy than trains-experts

By Basil Katz

NEW YORK, Nov 11 (Reuters) - U.S. truck operators are under pressure to improve energy efficiency as rail companies tout their green credentials and bid to win more freight haulage.

The American Trucking Association says trucks transport about 70 percent, or 10 billion tons of all U.S. freight annually. But they use at least three times as much energy as trains per ton carried, analysts say.

The recession cut the amount of freight hauled around the country more than 10 percent compared to last year, says the American Trucking Association. But that was a temporary blip.

"As we expect a tremendous increase in freight volume in the coming years, we believe there are significant economic, environment and efficiency benefits in moving as much of it as possible on rail," said Robert Sullivan, of CSX, the third-largest U.S. railroad by revenue.

The 2.2 million registered semi-trucks, which account for most U.S. heavy long-haul transportation, averaged 5.1 miles per gallon (8.2 km per 3.8 litres) in 2007, said the Center for Transportation Analysis at Oakbridge National Laboratory.

Rail companies, which would like to become a green alternative to trucking as the economic recovery gathers steam, were boosted when Warren Buffett's Berkshire Hathaway (BRKa.N) (BRKb.N) recently agreed to spend $26 billion to buy railroad operator Burlington Northern Santa Fe Corp (BNI.N).