(Reuters) -U.S. President Donald Trump on Sunday urged China to quadruple its soybean purchases ahead of a key tariff truce deadline, sending Chicago soybean prices higher, though analysts were quick to question the feasibility of any such deal.

In a late night post on Truth Social, Trump said China was worried about a shortage of soybeans and he hoped it would quickly quadruple its soybean orders from the U.S.

"Rapid service will be provided. Thank you President XI," Trump said in his post.

The most active soybean contract on the Chicago Board of Trade (CBOT) jumped 2.38% to $10.11 a bushel at 0637 GMT on Monday after Trump's post. The contract was steady earlier.

China, the world's largest soybean buyer, imported roughly 105 million metric tons last year, just under a quarter coming from the U.S. and most of the remainder from Brazil. Quadrupling shipments would require China to import the bulk of its soybeans from the U.S.

"It's highly unlikely that China would ever buy four times its usual volume of soybeans from the U.S.," said Johnny Xiang, founder of Beijing-based AgRadar Consulting.

A tariff truce between Beijing and Washington is set to expire on August 12, but the Trump administration has hinted that the deadline may be extended. It is unclear if securing China's agreement to buy more U.S. soybeans is a condition for extending the truce as Trump looks to reduce China's trade surplus with the U.S.

China's soymeal futures fell 0.65% to 3,068 yuan per metric ton on expectations U.S. imports could increase supply.

China's Ministry of Commerce did not immediately respond to a Reuters request for comment.

Under the Phase One trade deal signed during Trump's first term, China agreed to boost purchases of U.S. agricultural products, including soybeans. However, Beijing fell far short of meeting those targets.

This year, amid Washington-Beijing trade tensions, it has yet to buy any fourth quarter U.S. beans, fuelling concerns as the U.S. harvest export season approaches.

"On Beijing's side, there have been quite a few signals that China is prepared to forego U.S. soybeans altogether this year, including booking those test cargoes of soymeal from Argentina," said Even Rogers Pay, an agricultural analyst at Trivium China.

Reuters previously reported that Chinese feedmakers have purchased three Argentine soymeal cargoes as they aim to secure cheaper South American supplies amid concerns about a possible soybean supply disruption in the fourth quarter.

U.S. soybean industry has been seeking alternative buyers, but no other country matches China's scale. Last year, China imported 22.13 million tons of soybeans from the U.S., and 74.65 million tons from Brazil.