President Bush is on the verge of making good on a big campaign promise — rewriting the nation's domestic energy policy.

The president also still faces uncertainty over a Medicare (search) prescription drug package after Republicans received stronger-than-expected opposition from within the party's ranks and among Democrats.

GOP majorities in Congress vowed to deliver both bills before Thanksgiving.  House leaders took a big step toward that promise, getting the compromise energy bill passed Tuesday on a 246-180 vote.

The Senate took up the bill on Wednesday, and Senate Majority Leader Bill Frist, R-Tenn., said debate could last through the weekend and until early next week before all is said and done.

"For the past two years, the passage of a comprehensive national energy policy has been a top priority for my administration, and I commend the House for its vote today and urge the Senate to act expeditiously as well," Bush said Tuesday in a statement from London, where he is on a three-day trip. "America will be more prosperous and more secure when we are less dependent on foreign sources of energy. Reliable and affordable energy is critical to our economic security, our national security, and our homeland security."

But liberal Democrats criticized the bill and said the president's claims of self-sufficiency will not be reached based on the final bill.

"This energy bill is the single-worst public health, environmental, and energy security public policy disaster in a generation," said Rep. Ed Markey, D-Mass. "It is an appalling concoction of tax breaks, subsidies and pork barrel spending for wealthy, gas, nuclear, coal and utilities industries."

Markey said the bill does nothing to reduce dependence on oil, 70 percent of which is used for cars, trucks and SUVs in the United States.

"This energy legislation is a disservice to all the young men and women who are now in the Middle East protecting foreign oil," he said in a statement.

But supporters say it's no surprise the bill provides tax incentives for energy industries.

"Who else is going to produce energy in this country — Nancy Pelosi?" asked House Majority Leader Tom DeLay, referring to his Democratic counterpart.

The 1,400-page bill will cost an estimated $32 billion over 10 years — almost four times the price tag of the original White House proposal. It includes $5 billion in new spending on emerging energy technologies, such as hydrogen-powered cars and biomass. It puts another $25 billion into tax cuts and subsidies to increase the production of oil, natural gas and coal, and to boost supplies of nuclear, wind, solar and water power.

It also provides tax measures of $1.5 billion for conservation and efficiency programs including tax credits for energy efficient homes and hybrid gas-electric cars.

Energy Secretary Spencer Abraham said the administration would have preferred to see the costs lower but accepted the bill's tax package.

To avoid a repeat of last summer's blackouts that shut down the northeast United States for a night and even longer in some parts, the bill imposes new federal rules to guarantee electricity grid reliability.

Asked if Senate Democrats will push for a filibuster, Senate Minority Leader Tom Daschle, D-S.D., dodged the question.

"I'm not going to characterize whether I'm leaning, standing straight ... I think the most important thing to say is we've got to see the legislation," he said. 

Daschle's hesitation may arise from his representation of a corn-producing state. The bill calls for the doubling of the use of ethanol in gasoline to 5 billion gallons a year.

Democratic sources told Fox News that no filibuster is planned for the energy bill despite concerns about a gasoline additive, MTBE (search), that has been found to contaminate drinking water in at least 28 states. The bill would shield MTBE makers of liability in lawsuits unless they are found to be negligent in the handling of the product.

Democratic Sens. Charles Schumer of New York and Barbara Boxer of California said Tuesday they may filibuster the legislation in hopes of getting the MTBE measure removed. Schumer said three or four Republicans were ready to join the effort.

But Republicans said they weren't worried.

"I don't think it's a showstopper," Senate Majority Leader Bill Frist, R-Tenn., said of the MTBE issue.

Democrats are also debating what to do with the Medicare bill, which aims to provide drug coverage to 40 million Americans. The 10-year, $400 billion package stalled in the House after Republican leaders discovered gaps in GOP support and stiffening Democratic opposition.

A key issue for some lawmakers is a measure in the bill that would not allow for the reimportation of cheaper pharmaceuticals from Canada.

"It ain't over 'til it's over, and this debate is going to go on until ultimately, Americans have access to world class drugs at world market prices," said Rep. Gil Gutknecht, R- Minn.

Gutknecht is among at least three Republicans who vowed to vote against the bill unless GOP leaders rewrite it. With few votes to spare, those leaders took heed and delayed moving the bill to the floor.

The White House is leaning hard on Republicans and moderate Democrats to get the job done. Democrats say they are waiting to see if the GOP will re-write the Medicare drug bill. If it does, fresh votes will be taken and filibuster options re-examined.

Fox News' Major Garrett and The Associated Press contributed to this report.