It’s just 60 miles from El Dorado Dairy in Ontario, Calif., to the nation’s largest container port in Los Angeles. But the farm is having little luck getting its products onto a ship headed for the foreign markets that are crucial to its business.

The farm is part of one of the nation’s largest cooperatives, California Dairies Inc., which manufactures milk powder for factories in Southeast Asia and Mexico that use it to make candy, baby formula and other foods. The company typically ships 50 million pounds of its milk powder and butter out of ports each month. But roughly 60 percent of the company’s bookings on outbound vessels have been canceled or deferred in recent months, resulting in about $45 million in missed revenue per month.

“This is not just a problem, it’s not just an inconvenience, it’s catastrophic,” said Brad Anderson, the chief executive of California Dairies.

supply chain crisis for imports has grabbed national headlines and attracted the attention of the Biden administration, as shoppers fret about securing gifts in time for the holidays and as strong consumer demand for couches, electronics, toys and clothing pushes inflation to its highest level in three decades.

Yet another crisis is also unfolding for American farm exports.

The same congestion at U.S. ports and shortage of truck drivers that have brought the flow of some goods to a halt have also left farmers struggling to get their cargo abroad and fulfill contracts before food supplies go bad. Ships now take weeks, rather than days, to unload at the ports, and backed-up shippers are so desperate to return to Asia to pick up more goods that they often leave the United States with empty containers rather than wait for American farmers to fill them up.

The National Milk Producers Federation estimates that shipping disruptions have cost the U.S. dairy industry nearly $1 billion in the first half of the year in terms of higher shipping and inventory costs, lost export volume and price deterioration.

“Exports are a huge issue for the U.S. right now,” said Jason Parker, the head of global trucking and intermodal at Flexport, a logistics company. “Getting exports out of the country is actually harder than getting imports into the country.”

Agriculture accounts for about one-tenth of America’s goods exports, and roughly 20 percent of what U.S. farmers and ranchers produce is sent abroad. The industry depends on an intricate choreography of refrigerated trucks, railcars, cargo ships and warehouses that move fresh products around the globe, often seamlessly and unnoticed.

U.S. farm exports have risen strongly this year, as the industry bounces back from the pandemic and benefits from a trade deal with China that required purchases of American agricultural products. Strong global demand for food and soaring commodities prices have lifted the value of U.S. agricultural exports more than 20 percent over last year.

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A survey by the Agriculture Transportation Coalition, which represents exporters, found that 22 percent of foreign agriculture sales on average were being lost as a result of transportation challenges.

Delays at ports have particularly hurt products that move in corrugated metal containers, like cheese, butter, meat, walnuts and cotton.

One company, Talmera USA Inc., which exports milk powder, cheese and dairy ingredients like lactose, had a shipment delayed so many times that its load finally wound up on the original vessel it was assigned to after the ship had left the port in Seattle, circumnavigated Asia and returned weeks later.

Mr. Anderson said that his company’s customers were beginning to look to suppliers in Europe, New Zealand and other countries for their purchases, even though the U.S. dairy industry has a reputation for high quality. “Frankly none of that matters to the customer if we can’t get it there,” he said.

Part of the problem is that shipping companies are able to charge far more to ferry goods from Asia to the United States than vice versa, so they don’t want to waste time waiting for a less lucrative load departing from the West Coast.