U.S. soybean export premiums are at their highest in 14 months, as grain merchants race to ship out a record-large U.S. harvest ahead of the U.S. presidential election and fears of renewed trade tensions with top importer China, traders and analysts said.

Nearly 2.5 million metric tons of U.S. soybeans were inspected for export last week, including almost 1.7 million tons bound for China, the most in a year, according to U.S. Department of Agriculture data released on Monday.

But while this export flurry is a bright spot for U.S. farmers coping with low prices and hefty supplies, sellers say such heightened export demand could be short lived — leaving the U.S. with a glut of oilseeds at a time when prices are hovering near four-year lows.

Tariff threats from presidential hopeful Donald Trump's campaign speeches are prompting some Chinese importers to shun U.S. shipments from January onward, traders and analysts said.

Instead, these buyers are booking Brazilian soy - and paying up to 40 cents a bushel more than they would in the United States in an earlier-than-normal seasonal shift that's shrinking the U.S. export window.

"The Chinese don't know what final costs will be relative to tariffs. They are avoiding the United States from January forward," said Dan Basse, president of AgResource Co.

Basse said he expects 2024/25 U.S. exports to fall 75 million bushels short of the latest USDA forecast.

How China will respond to tariffs under a new U.S. administration is unclear. Trump has vowed to boost tariffs on Chinese products to around 60%, while challenger Kamala Harris' plan is to keep tariffs roughly as they are now.

"There's a threat of tariffs from either party, but more so under a Trump administration," said Terry Reilly, senior agricultural strategist with Marex. "With Harris, there's a real possibility that things will revert to the status quo."

Traders said premiums for immediate shipments of U.S. soy are likely to erode in the coming weeks as near-term demand is met and if trade war concerns limit new buying by China.

Cash premiums for soybean barges delivered to Gulf export terminals by midweek spiked to a 130-cent premium over Chicago Board of Trade November SX24 futures on Monday, reflecting strong demand for immediate supplies, traders said.

The same soybeans, if loaded next month, were available for 27 cents a bushel less, or a savings of roughly $14,000 per fully loaded 1,500-ton barge.