Rising market prices underscore the need for Dodd-Frank Act derivatives rules to curb speculation in commodities such as oil, gold and natural gas, Commodity Futures Trading Commission Chairman Gary Gensler told lawmakers.

“Though the CFTC is not a price-setting agency, rising prices for basic commodities highlight the importance of having effective market oversight,” Gensler wrote in response to a May 11 letter from 17 senators seeking a CFTC plan for curbing crude-oil speculation. Gensler's letter said he was writing on behalf of Commissioners Michael V. Dunn and Scott O'Malia.

Regulators and lawmakers have attempted to rein in speculation since 2008 amid concern that investors contributed to oil's rise to a record $147.27 a barrel. The CFTC has proposed so-called position limits in agricultural, metals and energy derivatives, under rulemaking authority granted by Dodd- Frank, the regulatory overhaul enacted last year.