Washington: Last year's roller coaster ride in commodity prices left the US Congress and federal regulators with a doozy of a headache in 2009 - what to do about speculators.

Soaring prices for everything from cotton to oil fuelled complaints of excess speculation.

Lawmakers, determined to prevent a recurrence, are looking to give the Commodity Futures Trading Commission more funding and authority. However, some say curbing speculators may make markets less efficient at setting prices and allocating risk.

Senate Agriculture Committee chairman Tom Harkin told Reuters the CFTC may need authority to rein in excessive speculators.

"That is something we're looking at," said Harkin, who added excessive speculation is hard to define. The CFTC "may already have the power to do that but maybe we need to spell it out in legislation."

He said over-the-counter financial transactions need to happen on regulated exchanges and there also must be higher margin calls and limits to make sure people have the money to back up their transactions.

The House Agriculture Committee already has approved a bill boosting CFTC oversight.