News that US President Donald Trump and China's Xi Jinping would not meet dashed hopes that the two sides were progressing on a deal to end a bitter trade fight that has slashed Chinese purchases of US soya.
Corn and wheat also retreated, pressured by technical selling and profit-taking as investors moved to the sidelines ahead of US crop data due on Friday, some of it delayed by the recent US government shutdown.
Earlier on Thursday, White House adviser Larry Kudlow said in an interview on Fox Business Network that there was a sizable distance to go in US-China trade talks.
Chicago Board of Trade March soyabeans fell 9 cents to $9.12-3/4 a bushel by 11:38 a.m. CST (1727 GMT). Technical selling as the contract broke below chart support at its 200-day moving average and recent lows around $9.13 accelerated losses. CBOT March wheat dropped 11-3/4 cents to $5.14-1/4 a bushel and March corn shed 2 cents to $3.78 a bushel. Selling accelerated as both contracts breached support at several key moving averages. Market participants were waiting for a long list of US Department of Agriculture (USDA) crop forecasts and estimates due on Friday after key reports were delayed due to the 35-day partial government shutdown.