The Senate voted 94-0 Tuesday to move ahead on legislation to curb speculation in oil markets.

But the accord didn't last long.

Shortly after the vote, word circulated that Senate Democrats cancelled upcoming markups in the Appropriations Committee on two bills that would force Democrats to take votes on GOP amendments to lift the offshore drilling ban, as well as the oil shale drilling ban.

Most Democrats — and their allies in the environmental movement — are opposed to lifting offshore restrictions. But enough of them have indicated they would defect for the GOP side to prevail on a simple up-or-down vote requiring only a margin of one to win. Democrats are, in effect, filibustering that — requiring 60 votes instead of 51 to prevail.

Speaker Nancy Pelosi, D-Calif., won't let the House or any of its committees or subcommittees allow a vote on offshore drilling. She and other Democrats say the oil companies should first look to areas offshore and in Alaska where drilling is already allowed.

Senate Appropriations Committee Chairman Robert Byrd, D-W.Va., joined her Tuesday, reversing course and calling off a vote planned for Thursday on a bill funding the Interior Department rather than lose a committee vote to Republicans on lifting the moratorium on new drilling on the Outer Continental Shelf.

Republicans on the committee sent a letter to Byrd urging him to reconsider.

"We are profoundly disappointed by the cancellation of this week's scheduled markup of the Fiscal Year 2009 Interior and Legislative Branch appropriations bills, and the second supplemental appropriations bill for Fiscal Year 2008," they said. "It is readily apparent that the markup was canceled entirely due to the majority's unwillingness to consider and vote on amendments relating to domestic energy production."

Republican Mississippi Sen. Thad Cochran, who is also on the committee, issued a separate statement saying, "the Democrats in charge of Congress are ignoring the calls of the American people and refusing to take a vote on this crucial issue."

The Senate bill on oil markets would require the Commodity Futures Trading Commission to set limits on trading in oil markets by investors and speculators and close a loophole that allows speculators trading on the London oil market to escape scrutiny by U.S. regulators.

Democrats say the rapid increases in oil prices have coincided with big rises in trading on oil future markets and investment in oil by pension and hedge funds. "The demand for 'paper barrels' ... has begun to swamp the price signals that are generated by the more traditional hedgers and the large producers and the consumers of petroleum products in tune to the real time dynamics of supply and demand," said Energy Committee Chairman Jeff Bingaman, D-N.M.

But any hope of bipartisanship to pass the bill is likely a mirage. The overwhelming majority to consider the bill only set up a debate in which both parties blame the other for not doing enough to combat this summer's $4-a-gallon gasoline prices.

Majority Leader Harry Reid, D-Nev., is offering Republicans only one amendment and a GOP filibuster seems likely. That's fine with Reid — a political draw even if the underlying oil speculation bill dies.

"The procedure is fine," Reid told reporters Tuesday. "The Republicans don't want to legislate."

Republicans want to offer an amendment to open the Outer Continental Shelf to oil drilling. GOP nominee-to-be John McCain is a new convert to such drilling, and opinion polls suggest voters are rallying around the idea.

"Nobody can say with a straight face that simply addressing speculation — a very narrow part of the problem — is a serious approach," said Minority Leader Mitch McConnell, R-Ky. He said Republicans will insist on a full and fair debate on a wide range of energy issues, including offshore drilling.

For Republicans, the drilling question is one of the few issues where they have an edge with voters, and they're pressing it to the hilt. Even though new offshore leases wouldn't deliver oil to the marketplace for a decade or so, many Republicans say simply opening up new coastal areas to exploration would lower prices now.

"If we move to demonstrate that we are opening up America's energy resources, that would factor into future expectations of where supply-and-demand go," said Rep. Eric Cantor, R-Va. "Those future prices are directly related to spot prices."

In a CNN/Opinion Research poll conducted last month, 73 percent of respondents said they favored an expansion of offshore drilling for oil and natural gas in protected U.S. waters.

With the public in favor of more drilling, House Democrats brought a bill they called the Drill Responsibly In Leased Lands Act — the DRILL Act— to the House floor last week in an effort to demonstrate that they, too, want more oil. The bill would have required oil companies to develop the leases they've purchased on federal lands and offshore in the Gulf of Mexico or forfeit them.

But Democratic leaders used a fast-track procedure requiring a two-thirds majority to pass. It didn't. The alternative requiring only a simply majority for passage would also have required giving Republicans a vote on their proposal to allow drilling off the Atlantic and Pacific coasts.

Similarly, Reid appears content to have Republicans and Democrats effectively filibustering each other's energy proposals.

Of course, there's no talk of putting off Congress' upcoming five-week recess — recently increased from the four weeks originally scheduled — to deal with energy issues.

"We're out of here in 10 days," Reid said Tuesday.

The Associated Press contributed to this report.