WASHINGTON -- President Bush yesterday called for lifting the 27-year ban on U.S. offshore oil drilling, joining Arizona Sen. John McCain in endorsing an idea that Republicans hope will gain traction in Congress and on the presidential campaign trail as the price of gasoline soars.

In a Rose Garden appearance, the president challenged Democrats to drop their "obstruction" of proposals to expand domestic energy production. "Americans will rightly ask how ... high gas prices have to rise before the Democratic-controlled Congress will do something about it," he said.

Democratic leaders in Congress said the plan is going nowhere. "President Bush and John McCain are not serious about addressing gas prices," said Senate Majority Leader Harry Reid, D-Nev. "If they were, they would stop offering the same old ideas meant to pad the pockets of Big Oil and work with Democrats to reduce our dependence on oil."

On Monday, Mr. McCain called for lifting the ban, reversing an earlier position and angering environmentalists whom he has sought to appeal to in his presidential campaign. Mr. Bush's announcement puts the weight of the White House behind the idea, but also gives Democrats another opportunity to link the presumptive GOP nominee to the unpopular president.

"McCain's capitulation to Big Oil could hurt him among independents and Clinton supporters, particularly in communities that depend on a clean ocean and beaches for their jobs and small businesses," said Daniel Weiss, an analyst at the liberal Center for American Progress Action Fund, referring to Democratic primary voters who backed New York Sen. Hillary Rodham Clinton.

But Republicans are taking heart in recent polling which suggests that the public may be more receptive to drilling, especially if it were coupled with other initiatives to address gas prices. A recent Gallup poll showed that 57 percent of respondents were willing to support drilling in the nation's coastal and wilderness areas currently closed to exploration.

"When drivers are paying $4 for a gallon of gas, and there's the perception that the economy's going to hell in a handbasket, voter attitudes regarding offshore drilling can change pretty quickly," said GOP pollster Neil Newhouse. "All of our evidence indicates that's exactly what's happened."

This view appears to be fueling the separate announcements from Mr. Bush and Mr. McCain this week that they want Congress to abandon its moratorium on offshore drilling. Mr. Bush has spoken favorably of drilling in the Gulf of Mexico before, but yesterday was the first time he indicated that he would rescind an executive-branch order banning all offshore drilling if Congress removed its own long-standing prohibitions.

The moratorium was imposed in 1981, when lawmakers from coastal states sought to block leasing off the Massachusetts and California coasts. Congress has approved the moratorium every year since.

President George H.W. Bush issued a separate executive order banning offshore oil drilling in 1991. That prohibition was initially slated to expire in 2002, but in 1998, then-President Bill Clinton extended it to 2012.

During his appearance yesterday, Mr. Bush again urged Congress to open Alaska's Arctic National Wildlife Refuge for oil drilling and to ease the regulatory obstacles to expanding refining capacity. Mr. McCain remains opposed to drilling in the refuge.

The president also called for ending a ban on oil shale drilling in the Rocky Mountain states, a move that he said might open access to about 800 billion barrels of recoverable oil, or three times the number of reserves that Saudi Arabia has. It has been considered too costly to develop those reserves, but Mr. Bush said the economic "calculus is changing."

Much of this agenda will prove controversial, especially in politically influential coastal states such as Florida and California, whose GOP governors diverge on the wisdom of drilling. Florida Gov. Charlie Crist, a key McCain ally, reversed his position this week and said he favors lifting the federal ban, giving states the option of drilling, while California Gov. Arnold Schwarzenegger yesterday restated his opposition to drilling off his state's coastline.

Keith Hennessy, director of the White House National Economic Council, said that under the president's plan, individual states would retain veto power.

Richard Charter, a consultant for Defenders of Wildlife Action Fund, said environmental and business groups have found common cause on the issue because pristine beaches generate so much tourism income.

But administration officials and others asserted that technology for preventing oil spills has improved, and that drilling can be done safely.

A major uncertainty is the economic impact of offshore drilling, which by Mr. Bush's estimate could result in an extra 18 billion barrels of oil -- equivalent to the nation's current oil production for the next 10 years, according to the White House. Mr. Hennessy said he thinks oil prices might fall as markets began building in expectation of a growing supply.

But the federal Energy Information Administration estimated that if leasing began in 2012, "access to the Pacific, Atlantic and eastern Gulf regions would not have a significant impact on domestic crude oil and natural gas production. or prices before 2030."