“There’s not a bank in the United States that’s going to loan money to that customer of mine in Argentina to buy my airplane,” said David Ickert, vice president of finance at Air Tractor, which makes crop-dusting and firefighting airplanes in Olney, Tex. “There is not a free-market system that operates like that. It does not exist. We need the Ex-Im Bank, period.”

Like so much else in Congress these days, it is not that simple.

With its charter set to expire in May, the bank is the target of conservative groups. They are making the case to Republicans that the bank, created in 1934 to finance sales to the Soviet Union, has no place in a free-market system. Club for Growth is holding it up as the next Fannie Mae or Freddie Mac, crowding out private lending and offering dangerous loans that ultimately could be left in the laps of the taxpayer.

“Those groups are just wrong, period,” said Jay Timmons, president of the National Association of Manufacturers and a generous personal contributor to Republican candidates.

The bank is financed with a small percentage of each loan it makes to foreign buyers of American exports, producing $3.4 billion in profits for the federal government over the last five years.

Drew Greenblatt, president and owner of Marlin Steel Wire Products, in Baltimore, said he recently got a rush order for wire baskets from a firm in Singapore, assuming he could finance the sale. He went to the Export-Import Bank and paid a one-half-percent fee on the loan. The bank guaranteed 95 percent of the loan. He kept the plant working through the weekend and completed the sale.

“Think about all the winners in this transaction,” he said. “Ex-Im got half a point. Baltimore City steelworkers got extra hours. I got extra profits to meet payroll, and hopefully I got a client who will reorder from me.”

If anything, the anger over the stalled transportation bill is even more acute, business lobbyists say. The Senate, in a bipartisan vote, has passed a surface transportation bill that would keep money flowing for two years. The House, however, appears stuck.