U.S. soybean futures are expected to start at their lowest level of the year Friday as mounting economic woes fuel selling across asset classes.

Traders predict soybeans for November delivery, the most actively traded contract, will sink 15 cents to 20 cents a bushel at the Chicago Board of Trade when trading begins at 10:30 a.m. EDT. In overnight electronic trading, the contract tumbled 20 3/4 cents, or 1.6%, to a 10-month low of $12.62 1/4 a bushel.

Driving prices lower is widespread selling of equities and commodities that's fueling investor fears of an economic slowdown. The broad-based selling extends sharp losses from Thursday, when soybeans sank 5.2%.

"Outside markets continue to pressure our markets," said Jason Holthaus, analyst for Country Hedging, an agricultural commodity brokerage in Minnesota.

This week's slide in prices adds to a recent setback in agricultural markets. Soybean futures have pulled back 13% since the nearby contract reached a three-year high in late August on concerns about low inventories.

The latest economic worries have been hitting farm prices worldwide. Argentine soybean prices took a beating this week as the sell-off in global equities markets spilled over to commodities, with trading grinding to a halt Thursday as sellers refused to take low bids. Soybean futures on China's Dalian Commodity Exchange also fell sharply Friday.

"The markets are moving in macro step with the liquidation theme," wrote analysts for AgResource Company, an agricultural consultancy in Chicago.

Yet, demand from users of soybeans could help slow the decline in prices. The U.S. Department of Agriculture on Friday said private exporters struck deals to sell 126,000 metric tons of soybeans to China, the world's top importer of the oilseed. China appears to view the sell-off as a buying opportunity, as the USDA had already reported deals for 300,000 tons earlier this week.