Barack Obama: "There will be those who strongly disagree with this decision"
Oil firms could be given the chance to explore for reserves off the US coast for the first time in decades, under plans outlined by President Obama.
The White House says drilling will be allowed off Virginia and considered off much of the rest of the Atlantic coast.
The plans would overturn moratoriums on exploration put in place in the 1980s.
Analysts say the move, designed to cut dependency on foreign oil, is aimed at appeasing Republicans to help pass Mr Obama's climate-change proposals.
The Democrat-backed climate change bill, which calls for binding emissions' limits, has been languishing in Congress for months amid Republican opposition.
Steve Kingstone, BBC News, Washington
President Obama will draw criticism from environmental groups and influential politicians in coastal states but his eyes are on a bigger prize: a climate change bill, compatible with any post-Kyoto international agreement.
Together with earlier concessions on coal and nuclear power, Wednesday's announcement is an attempt to secure opposition Republican votes in the Senate, which will be needed if the bill is to become law.
Critics will say Mr Obama has given Republicans what they wanted. The administration counters that responsible exploration on the home front will lessen America's dependency on oil from unpredictable foreign suppliers.
The president also placed drilling in the context of a broader commitment to renewable energy, which he says will create or save 700,000 jobs.
As so often in presidential politics, achievements hinge on successfully balancing competing forces. Mr Obama just walked out on to the high-wire.
But Republicans have opposed much of Mr Obama's domestic agenda, and were quick to dismiss his oil drilling plans.
John Boehner, Republican leader in the House of Representatives, welcomed the end of the moratorium in the east, but said keeping the ban on other areas "makes no sense".
Environmental campaigners also denounced the plans, with Greenpeace saying it added to the US "addiction to oil".
"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," said the group's Phil Radford.
Moratoriums on drilling were put in place amid fears that an oil spill would cause an ecological disaster.
Many Democrats oppose any expansion of oil drilling, but Mr Obama has spoken in favour of such a move in the past.
Announcing the proposals, he stressed that drilling alone would not meet the nation's energy needs.
"Today 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 at Andrews Air Force Base, Maryland.
"My administration will consider potential new areas for development in the mid and south Atlantic and the Gulf of Mexico."
The White House also announced a mixed package for Alaska - cancelling outright oil and gas drilling leases in the Bristol Bay area.
Four leases in the Chukchi and Beaufort Seas off Alaska's north coast were also cancelled - although the area will be left open for "future scientific research to assess their suitability for leasing".
A previously announced lease sale in Alaska's Cook Inlet would be allowed to go ahead, the government said.
1: Four pending leases cancelled and scientific assessments carried out
2: Lease for Bristol Bay area cancelled to protect "sensitive area"
3: Drilling could be allowed in Eastern Gulf if moratorium expires
4: First new offshore sale in the Atlantic in more than two decades
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