KANSAS CITY — A nearly 3% decline this week in May soybean futures prices has mostly factored in any news of Chinese cancellations of U.S. cargoes of the oilseed, said Karl Setzer, grain analyst with Max Yield Cooperative in West Bend, Iowa.

May soybeans started the week trading at about $14.09 a bu but were trading below $13.80 a bu by mid-morning March 12, up from early session lows of $13.65½ a bu. Still, prices were up nearly 15% since the end of January.

The swooning soybean futures market this week was trading on rumors that China has cancelled up to 20 cargoes of South American soybeans and will soon cancel an undetermined number of U.S. cargoes, Mr. Setzer said. He added that profit-taking by commodity funds with large long positions also was driving prices lower. He said market participants are nervous about a weakening Chinese economy, which might mean a longer-term decline in demand from the second-largest economy in the world.

Mr. Setzer said he expected Chinese cancellations of U.S. soybeans to be limited because China relies on imports to meet its huge demand for soy products. He added that many shipments of U.S. soybeans already have freight contracted to transport the oilseed to China and “it is extremely difficult to wash out of those obligations.”

South America will start ramping up soybean exports later this week, which will keep the U.S. market on edge because of expectations that cheaper Brazilian and Argentinian soybeans will crowd out demand for U.S. supplies, Mr. Setzer said. He added that South American ports appeared to be functioning well and logistics weren’t likely to be a major liability.

Mr. Setzer said it would take some show-stopping news later this week to send soybeans sharply lower from current levels. The March 13 U.S. Department of Agriculture export sales report for the week ended March 6 may document some cancellations of soybean exports and will be closely watched by the markets, he said.

He contended that a little less buying from China might actually be beneficial for the U.S. soybean market because 2014 carryout is so tight and it is possible the U.S. could run out of supply for domestic needs if exports remain robust.