WASHINGTON (Reuters) - The Senate on Tuesday voted overwhelmingly to open debate on a bill to rein in energy market speculation blamed for high oil and gasoline prices.

A man fills up his truck with gas at a gas station in Santa Monica, California, May 28, 2008. REUTERS/Lucy Nicholson

But final passage of the legislation looked difficult because of disagreements between its Democratic backers and Republicans who want to include other provisions designed to boost domestic oil production.

With 60 votes needed to proceed with the measure, 94 of the 100 U.S. Senators voted “yes” and none against. But Republicans still may block final approval unless amendments are added to expand offshore drilling and develop oil shale fields.

Democrats oppose opening closed areas to drilling, saying oil companies first should explore millions of government acres they have already leased.

The legislation would require institutional traders to give regulators more details on unregulated over-the-counter transactions, to guard against price manipulation or excessive speculation.

The Commodity Futures Trading Commission also would review trading practices of swaps dealers and commodity index funds.

The legislation would not require higher margins to buy and sell oil, as the futures industry had feared. But it would limit the number of oil contracts speculators could control.

Senate Majority Leader Harry Reid, a Nevada Democrat, said the legislation would help bring down fuel costs.

“If we did nothing else but pass this speculation bill, the American people would be very, very happy and the markets would be struck quickly and the price of oil would go down,” he said.

But Senate Republican Leader Mitch McConnell called restrictions on speculation “a very little piece” of the solution. “Americans will continue to demand a serious solution that gets at supply and demand; nothing less than that can be seen as a solution,” he said.

Reid has proposed that Democrats and Republicans offer one amendment each to the speculation bill, but Republicans have indicated they may offer as many as 28, dealing with matters from production to conservation.

Asked if he saw any possible “middle ground,” Reid told reporters, “No, I don’t.”

Congress will soon be leaving for its August recess, and time is running out to deal with the legislation.

Democrats are ready to offer their own oil production proposal that would speed up awarding government leases on areas already open to exploration. It also would take leases away from companies that don’t drill on them and put some oil from the Strategic Petroleum Reserve into the market.

The White House expressed disappointment with the Senate bill, because it does not increase domestic oil production.

White House press secretary Dana Perino said the “root cause” of high fuel costs is tight supply and growing demand.

“It is critical that we start focusing on the (oil) resources we have in our own country,” Perino said.

In related matter, an interagency task force headed by the CFTC said in a report that high oil prices were due to supply and demand factors, and speculators were not to blame.

CFTC commissioner Bart Chilton said he disagreed with the task force’s findings and supported the Senate legislation.

“I think its time that we sort of rein in what is becoming apparent, that it’s excessive speculation in the energy markets that are causing gas and oil prices to increase like we’ve never seen before,” he said Tuesday on the CSPAN.

Chilton noted that big hedge funds, pension funds and other speculators have invested $250 billion in commodities markets.

“People know at the gas pump that something’s going on.”