Countries such as Brazil and Canada are increasing soybean sales to China after Beijing last month threatened a 25 percent tariff on imports of U.S. soybeans, Bunge Chief Executive Soren Schroder said in an interview. The nation's farmers rely on China as the top buyer of U.S. soybeans, but at a current price of $420 (309 pounds) per ton, that translates to a potential tax of more than $100 per ton.

"Nobody's willing to take the risk of committing to U.S. soybeans to China in the current context, knowing that there could be a $100 penalty from one day to the other, and no way of managing that risk," Schroder said after the company reported a quarterly loss.

Soybeans were the United States' most valuable agricultural export last year to China, which bought $12 billion of the crop.

Freshly harvested South American soybeans typically dominate the world trade in the first half of the calendar year, followed by the United States from September onwards.

But U.S. soybean sales to China over the last four weeks are down 10 percent from this time a year ago, according to U.S. trade figures. That's a blow to U.S. farm country, which helped propel U.S. President Donald Trump into office two years ago.

Growing trade disputes are disrupting the agricultural supply chain worldwide and causing farmers and manufacturers to back away from expansion plans due to steel and aluminium tariffs.

"The trade stuff has been another layer of uncertainty that nobody really knows how to price yet," Schroder said.

Separately, Beijing slapped hefty anti-dumping deposits on U.S. imports of a livestock feed known as sorghum, and has also threatened duties on other U.S. products.

Bunge's rival, Archer Daniels Midland, said on Tuesday it would take a $30-million hit in the second quarter due to the sorghum trade dispute.

Bunge has seen trade flows shift amid renegotiations of the North American Free Trade Agreement, as well. In one example, Bunge milled wheat that had been imported to Mexico from Argentina as a test, Schroder said.

Mexican buyers imported ten times more corn from Brazil last year due to concerns that NAFTA renegotiations could disrupt their U.S. supplies.

The shift in China's soybean business is not a net negative for Bunge because it has operations globally, including in Brazil, Schroder said.

"If there is a problem in one part of the world, we can solve it in another," he said.

BUNGE SEES MARGIN IMPROVEMENT

Bunge reported a net loss of $21 million, or 20 cents per share, in the quarter ended March 31, down from a profit of $47 million, or 31 cents a share, a year ago. The loss included a $120 million charge due to forward oilseeds crushing contracts, which Bunge said would be offset in coming months.

Higher margins for soybean crushing should boost earnings significantly this year, executives said, after a severe drought reduced harvests in Argentina, the world's top exporter of soy products.

The margin increase prompted Bunge to raise its full-year earnings outlook for its agribusiness unit to a range of $800 million to $1 billion, from $550 million to $700 million.

Shares were up 3 percent at $73.81 in afternoon trading.

Bunge's projection for stronger performance was a turnaround after years of bumper harvests reduced price volatility and clipped margins for the company and its rivals, making it tough to turn a profit on their core business: buying, processing and selling corn, soy and wheat.

(Additional reporting by Uday Sampath in Bengaluru; Editing by Nick Zieminski)

By Tom Polansek