BEIJING/SINGAPORE/CHICAGO (Reuters) -U.S. farmers are missing out on billions of dollars of soybean sales to China halfway through their prime marketing season, as stalled trade talks halt exports and rival South American suppliers step in to fill the gap, traders and analysts said.

Chinese importers have booked around 7.4 million metric tons of mainly South American soybeans for October shipment, covering 95% of China's projected demand for the month and 1 million tons for November, or about 15% of expected imports, according to two Asia-based traders.

By this time last year, Chinese buyers had booked around 12 million to 13 million tons of U.S. soybeans for September-November shipment, said one of the traders, who is based in Singapore at an international trading company.

The U.S. normally ships most of its soybeans to China between September and January, before Brazil's harvest hits the market, but Chinese buyers have yet to book any U.S. cargoes for the new crop year, according to traders tracking shipments.

The U.S. sold some 22.9 million tons of soybeans to top buyer China in the marketing year that ran through August 2025. China purchased $12.8 billion of U.S. soybeans in 2024.

"If you look at the way things are, we think it is going to be South American beans through the end of the year," the Singapore trader said.

The prolonged absence of Chinese buying is expected to weigh further on benchmark Chicago soybean futures, already hovering near five-year lows.

U.S. soybeans are about 80 to 90 cents a bushel cheaper than Brazilian soybeans for September-October shipment, but China's 23% tariff on U.S. shipments adds $2 a bushel to the cost for importers, traders said.

The traders asked not to be named because they are not authorised to speak to media.

While other countries have been booking U.S. soybeans, Dan Basse, president of AgResource Co in Chicago, estimates that if China keeps out of the U.S. market until mid-November, total lost sales to the country could be as high as 14 million to 16 million tons.

The U.S. Department of Agriculture is likely to start trimming its 2025/26 U.S. soybean export forecast in its monthly World Agriculture Supply and Demand Estimates report on Friday, with further revisions likely if the trade war goes unresolved, he said.

In its previous outlook, the USDA pegged U.S. soybean exports at 46.4 million tons for 2025/26, already down from 51.02 million tons a year ago.

AWAITING TRADE PACT

Still, China has not completely closed its doors to U.S. soybeans, with plenty of purchasing still to be done for delivery in November through January.

"U.S. soybeans are currently attractively priced for many non-Chinese buyers, especially with limited competition during the peak selling season," said Johnny Xiang, founder of Beijing-based AgRadar Consulting.

"In contrast, strong Chinese demand has driven Brazilian soybean prices higher as their selling season winds down. If a China-U.S. trade deal is reached, the outlook for U.S. soybeans could improve significantly."

Expensive Brazilian soybeans threaten profits for Chinese oilseed processors, with crush margins in Rizhao, China's key processing hub, turning negative in the past two weeks after being positive in early August.

China's soybean imports hit record highs during May, June, July and August, boosting inventories, partly as a hedge by buyers against potential fourth-quarter supply disruptions.

"There's not much to say on China right now," said one U.S. soybean exporter. "If these were normal times, we'd be doing 15 cargoes a week."