United States Oil Fund ( USO) -1.5% Oil prices retreated during Monday's trading, dipping below $85 per barrel. Concerns regarding the Greece bailout helped pressure the euro against the dollar, making the commodity more expensive for Europeans. USO had a nice weeklong run heading into April that helped power the ETF to new 2010 highs. However, since the start of the month, the fund's performance has been noticeably choppy, dipping close to its 50-day moving average. Market Vectors Vietnam ETF ( VNM) -1.4% The wildly volatile Vietnam ETF is taking a hit today after two consecutive days of gains. Looking to the future, inflation may prove to be a weight on this nation's markets. According to a report from Citigroup ( C), there is a good chance that Vietnam's inflation could surpass 10% this year. All prices as of 2:15 p.m. EST -- Written by Don Dion in Williamstown, Mass.