Speaking at Andrews air base outside Washington, Mr. Obama said, "This is not a decision that I've made lightly." He addressed the expected outcry from disappointed environmentalists by saying he had studied the issue for more than a year and concluded it was the right call given the nation's voracious thirst for energy and the need to produce jobs and keep American businesses competitive.
"We're announcing the expansion of offshore oil and gas exploration but in ways that balance the need to harness domestic energy resources and the need to protect America's natural resources," Mr. Obama said, standing in front of a Navy F-18 fighter scheduled to fly on Earth Day with a half-biomass fuel mix.
The president said his decision is part of a broader strategy that also includes expanding the production of nuclear power and clean energy sources, to "move us from an economy that runs on fossil fuels and foreign oil to one that relies more on homegrown fuels and clean energy."
"The only way this transition will succeed is if it strengthens our economy in the short term and the long run," the president said. "To fail to recognize this reality would be a mistake."
Mr. Obama made no secret of the fact that one factor in his decision was attracting Republican support for a sweeping climate change bill that has languished in Congress. "Drill, baby, drill" was a mantra of the GOP during the 2008 presidential campaign.
"While our politics has remained entrenched along worn divides, the ground has shifted beneath our feet," the president said. "Around the world, countries are seeking an edge in the global marketplace by investing in new ways of producing and saving energy."
But Mr. Obama also has long been up front about his support for expanding offshore drilling as well as other energy sources less popular with die-hard environmentalists. In his State of the Union speech, he said he wanted the United States to build a new generation of nuclear power plans, invest in new coal technologies and make "tough decisions about opening new offshore areas for oil and gas development."
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The plan modifies a ban that for more than 20 years has limited drilling along coastal areas other than the Gulf of Mexico. It allows new oil drilling off Virginia's shoreline and considers it for a large chunk of the Atlantic seaboard.
Mr. Obama's blueprint would allow Interior to go ahead with oil and gas leases on tracts 50 miles off the coast of Virginia. Those leases had been approved for development but were held up by a court challenge and a departmental review.
In addition, the Interior Department has prepared a plan to add drilling platforms in the eastern Gulf of Mexico if Congress allows that moratorium to expire. Lawmakers in 2008 allowed a similar moratorium to expire; at the time President George W. Bush lifted the ban, which opened the door to Mr. Obama's change in policy.
It would allow exploration along the south Atlantic and mid Atlantic Outer Continental Shelf "to support energy planning" a step toward potential leasing.
At the same time, the president also announced that proposed leases in Alaska's Bristol Bay would be canceled. And the Interior Department is reversing last year's decision to open up parts of the Chukchi and Beaufort seas. Instead, scientists would study the sites to see if they're suitable to future leases.
Mr. Obama is allowing an expansion in Alaska's Cook Inlet to go forward. The plan also would leave in place the moratorium on drilling off the West Coast.
Under Mr. Obama's plan, drilling could take place 125 miles from Florida's Gulf coastline if lawmakers allow the moratorium to expire. Drilling already takes place in western and central areas in the Gulf of Mexico.
The climate change bill has remained elusive.
The president met with lawmakers earlier this month at the White House about a bill cutting emissions of pollution-causing greenhouse gases by 17 percent by 2020. The legislation would also expand domestic oil and gas drilling offshore and provide federal assistance for constructing nuclear power plants and carbon sequestration and storage projects at coal-fired utilities.
The president's Wednesday remarks were paired with other energy proposals that were more likely to find praise from environmental groups. Some 5,000 hybrid vehicles have been ordered for the government fleet. And on Thursday, the Environmental Protection Agency and the Transportation Department are to sign a final rule that requires increased fuel efficiency standards for new cars.