American Trucking Associations sent a letter Tuesday to the Commodities Future Trading Commission asking it to reduce offshore oil speculation that drives up the price of diesel and other end fuels.

Trucking and fuel industry officials said a new commodity trading rule is “too weak” to curb the excessive speculation in world oil markets that causes dramatic price swings.

A coalition of oil users that includes American Trucking Associations is urging Congressional leaders to “fully fund and defend” provisions of the financial reform law that would curb excessive speculation in oil futures.