Chicago Board of Trade soft red winter wheat futures firmed on Tuesday as weakness in the dollar sparked a mild short-covering bounce, traders said. A falling dollar makes US commodities a safe haven for investors looking for a hedge against inflation. But the gains were kept in check by ample global supplies, which continue to act as a damper on overseas demand for US supplies. The benchmark CBOT September contract hit resistance at its 40-day moving average, a level it hast not traded above since June 21. MGEX spring wheat and K.C. hard red winter wheat posted modest declines. Resistance for MGEX September spring wheat was noted near Monday's high.