BEIJING (Reuters) -U.S. protectionism is undermining agricultural cooperation with China, Beijing's ambassador to Washington said, warning that farmers should not bear the price of the trade war between the world's two largest economies.

"It goes without saying that protectionism is rampant, casting a shadow over China-U.S. agricultural cooperation," said Xie Feng, according to the transcript of a speech published by the Chinese embassy on Saturday.

Agriculture has emerged as a major point of contention between China and the U.S. as the superpowers are locked in a tariff war launched by President Donald Trump.

China in March slapped levies of up to 15% on $21 billion worth of American agricultural and food products in retaliation for sweeping U.S. tariffs. Washington and Beijing this month extended a truce for 90 days, staving off triple-digit duties on each other's goods.

U.S. agricultural exports to China fell 53% in the first half of the year from the same period in 2024, with a 51% decline in soybeans, Xie said in the speech to a soybean industry event in Washington on Friday.

"American farmers, like their Chinese counterparts, are hardworking and humble," Xie said. "Agriculture should not be hijacked by politics, and farmers should not be made to pay the price of a trade war."

The envoy said agriculture is a promising area of cooperation and a "pillar of bilateral relations". China has a comparative advantage in labour-intensive products, while the U.S. excels in land-intensive bulk commodities through mechanised, large-scale production, he said.

Last month U.S. Agriculture Secretary Brooke Rollins said Washington would curb farmland purchases by "foreign adversaries," including China.

The Department of Agriculture said it had fired 70 foreign contract researchers after a national security review intended to secure the U.S. food supply from adversaries including China, Russia, North Korea and Iran.

Xie dismissed the U.S. concerns. "Chinese investors hold less than 0.03% of U.S. agricultural land, so where does the claim of 'threatening U.S. food security' even come from," he said, calling the U.S. restrictions a "political manipulation".

U.S. soybean exporters risk missing out on billions of dollars worth of sales to China this year as trade talks drag on and buyers in the top oilseed importer lock in cargoes from Brazil for shipment during the key U.S. marketing season, traders say.