"Suddenly we're looking at GDP right around 2%," he said in an interview. "At that 2% level on GDP, we're very close to stall speed on the economy."

Some pullbacks are under way. American Airlines parent AMR Corp. and Delta Air Lines Inc. are trimming planned growth in seating capacity to blunt fuel expenses, even with the boost from more fare increases this year than in all of 2010.

"Rising gas prices and still-high unemployment levels weigh on the minds of our customers," Bill Simon, CEO of U.S. operations for Wal-Mart Stores Inc., said on a conference call on Feb. 22. "These issues affect discretionary spending and figure into our assessment for guidance."

The Bentonville, Ark.-based retailer has posted seven straight quarters of declining same-store sales in the U.S., and it forecast a drop in such revenue this quarter of as much as 2% from a year earlier.

Boyd Gaming Corp. expects that gamblers eventually may need some reassurance to help overcome any reluctance to pay more to drive to one of the Las Vegas-based company's casinos.

'Psychological Aspects'

"I'm sure you'll start to see promotions around gasoline and other things as part of a marketing campaign," Chief Operating Officer Paul Chakmak told analysts on a conference call on March 1. "People are generally fairly resilient, other than the psychological aspects of it."

Pump prices in some states are approaching the $4-a-gallon mark, topped by the $3.90 average in California and $3.88 in Hawaii through yesterday, according to AAA's website. Retail diesel fuel climbed to $3.88 a gallon, up 17% this year, according to AAA.

"Our near-term concern is more for our customers," Deere's Allen said in an interview. The product lineup at Moline, Ill.-based Deere includes lawnmowers, grain harvesters and construction equipment, some running on gasoline and others on diesel fuel.

For Boise Inc., a maker of paper and packaging, each 50- cent increase in diesel fuel means the loss of $8 million in earnings before interest, taxes, depreciation and amortization, Chief Financial Officer Samuel Cotterell said.