The case filed with the World Trade Organization rattled commodity markets as traders feared that an escalating trade war was on the way.
On the New York Mercantile Exchange, West Texas Intermediate crude oil for October delivery, which had finished at $98.97 Friday and started Monday morning at $99.31, closed the day at $96.95 per barrel.
Natural gas traded up and down, adding 1 penny in after-hours trading to $2.878 per million British thermal unit.
Home heating oil shed 0.28 cents to $3.1606 per gallon. Reformulated blendstock gasoline added 1.13 cents to $2.9546 per gallon.
At the pump, the average price for a gallon of regular unleaded gasoline was $3.862 per gallon, down from Sunday's $3.864, AAA reported.