The president's plan, announced at Andrews Air Force Base outside Washington on Wednesday, would see new tracts of the Atlantic off the Virginia coast opened to exploration, and expand leases for prospecting in the Gulf of Mexico off the coast of Florida.
Scientific research off Alaska in the Chukchi and Beaufort seas will also be authorised, but four pending lease sales approved under a previous Bush administration plan in those waters will be cancelled.
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Exploration will be barred in Bristol Bay in the eastern Bering Sea, a crucial habitat for sockeye salmon and other wildlife.
"In the short term, as we transition to cleaner energy sources, we'll have to make tough decisions about opening new offshore areas for oil and gas development in ways that protect communities and coastlines," Obama said.
Cap and trade plan
Obama portrayed the decision as part of a comprehensive energy plan, designed to wean the United States off foreign energy sources from volatile areas, and develop a new green economy.
"The bottom line is this: given our energy needs, in order to sustain economic growth, produce jobs, and keep our businesses competitive, we're going to need to harness traditional sources of fuel even as we ramp up production of new sources of renewable, homegrown energy."
The announcement comes at a time when Democratic plans to pass "cap and trade" legislation to cut greenhouse gas emissions face uncertainty in Congress as the economic crisis lingers in a mid-term election year.
Republicans, who have marched in lock step to oppose almost all of Obama's domestic agenda, back wider exploration of untapped US reserves, and adopted a "Drill, baby, drill," mantra during the 2008 presidential campaign.
But party leaders argued Wednesday that Obama's plan was too limited in scope, while some energy industry advocates complained the administration was not lifting a ban on oil prospecting off the northeast and Pacific coasts.
"Today's announcement is a step in the right direction, but a small one that leaves enormous amounts of American energy off limits," said Senate Republican minority leader Mitch McConnell.
'Environmental catastrophe'
Representative Doc Hastings, the top Republican on the House Natural Resources Committee, complained the plan would make Americans wait longer and get less in terms of jobs and energy.
"Hardly anyone would consider that a good deal - in fact, most would probably call it a clever trick," Hastings said.
The announcement ushered in delicate political decisions for lawmakers in both parties, some of whom want an expansion of drilling by coastal oil industries in their states, and others who fear environmental consequences.
Democratic Representative Frank Pallone of New Jersey warned on his Twitter feed that "offshore drilling on the Atlantic Coast invites an environmental catastrophe that would have severe economic consequences for New Jersey".
Environmentalists also criticised Obama's plan, some warning that the prospect of future drilling in the Beaufort and Chukchi seas could threaten prime polar bear habitats.
'Flawed, outdated policy'
"Today's announcement is unfortunately all too typical of what we have seen so far from President Obama - promises of change, a year of 'deliberation,' and ultimately, adoption of flawed and outdated Bush policies as his own, said Brendan Cummings, senior counsel at the Centre for Biological Diversity.
"Rather than bring about the change we need, this plan will further our national addiction to oil and contribute to global warming, while at the same time directly despoiling the habitat of polar bears, endangered whales, and other imperiled wildlife."
Greenpeace executive director Phil Radford also criticised the plan.
"Expanding offshore drilling in areas that have been protected for decades threatens our oceans and the coastal communities that depend on them with devastating oil spills, more pollution and climate change," he said.
But the energy industry applauded the decision.
"If the proposed areas ultimately end up being leased, it will represent the most significant increase in access to domestic energy from our oceans in decades," said Randall Luthi of the National Ocean Industries Association (NOIA).
