Oil prices are near 9-month highs in part because of concerns in the Middle East. Iran has threatened to close key oil shipping lanes through the Strait of Hormuz and last month halted crude oil deliveries to Great Britain and France.
The move was largely symbolic as London stopped buying Iranian crude last year, though market jitters helped drive oil prices higher.
U.S. Rep. Ed Markey, D-Mass., ranking member of the House Energy and Commerce Committee, accused Republicans of trying to block rules that would limit speculation in the commodities market.
Markey, in a statement, said there's a "wild West" mentality on Wall Street. Traders, he said, are exploiting global events to make a profit and U.S. consumers are paying the price.
"Wall Street speculators have turned the oil market into a crude oil casino where the American driver is now on the losing side of the bet," he said.
Markey had called on U.S. President Barack Obama to tap into the Strategic Petroleum Reserve in an effort to lower gasoline prices in the United States. The Obama administration, however, said there's no "magic bullet" that would influence prices.