WASHINGTON – In a bid to solidify his environmental legacy, President Barack Obama is expected to announce Tuesday that he will use his executive authority to issue a permanent ban on offshore drilling in federal waters off the southern Atlantic coast and in the Arctic.

Obama is considering invoking the 1953 Outer Continental Shelf Lands Act, a provision that gives presidents the ability to guard federal waters from future oil industry leases and drilling, said sources in the government who declined to speak on the record because the president was not yet ready to announce his plans.

Although the president and his aides haven’t commented on his intentions because it’s reportedly tied to a similar announcement by Canada, there is a news briefing scheduled at 4 p.m., and numerous environmental groups that pushed for the action have already issued statements expressing support.

Sources say U.S. and Canadian officials have been negotiating for months over whether they could reach a joint understanding on how to manage adjacent areas in the ocean, in an effort to make the new protections as sweeping and politically durable as possible.

Several advocacy groups have been lobbying Obama to ban oil and gas leasing in the Arctic entirely. Obama already invoked the Outer Continental Shelf Lands Act to safeguard Alaska’s Bristol Bay in 2014, and again last year to protect part of Alaska’s Arctic coast.

In the weeks since the election, the administration has moved swiftly to finalize a series of environmental safeguards, from imposing tighter curbs on oil and gas drilling on federal land to denying the renewal of a mining lease near Minnesota’s Boundary Waters Canoe Area Wilderness. As he prepares to leave the White House, Obama and his administration have adopted numerous rules to protect the environment, as recently as Monday when the Interior Department announced stricter regulations on the coal industry to protect streams.

The little known Outer Continental Shelf Lands Act was passed by Congress in August 1953 and asserted that “the outer Continental Shelf is a vital national resource reserve held by the federal government” for the public, and is “subject to environmental safeguards, in a manner which is consistent with the maintenance of competition and other national needs.” Management of the continental shelf federal lands is under the authority of the Bureau of Ocean Energy Management at the Interior Department.

Worried that the incoming Trump administration might move to exploit sensitive areas with oil and gas exploration, environmentalists have pushed the president to protect natural resources. In a statement, Jacqueline Savitz, Oceana’s senior vice president for the United States, virtually thanked the president in anticipation of his announcement.

Savitz called any potential act to safeguard the Atlantic from drilling “a smart business decision, based on science and facts. This decision would help to protect existing lucrative coastal tourism and fishing businesses from offshore drilling, which promises smaller, short-lived returns and threatens coastal livelihoods.”

An earlier plan to allow limited drilling off the Atlantic coast was shelved after state governments along the southern Atlantic coasts – including Virginia, North Carolina, South Carolina and Georgia – expressed worries over the impact on their beaches, tourist industry and environmentally sensitive marsh.

The Navy also objected. The Pentagon provided Interior with a map “that identifies locations . . . areas where the [Defense’s] offshore readiness activities are not compatible, partially compatible or minimally impacted by oil and gas activities,” spokesman Matthew Allen said. The map included nearly the entire proposed drilling area.

Live training exercises are conducted off the Atlantic Coast, “from unit level training to major joint service and fleet exercises,” Allen said in a statement. “These live training events are fundamental to the ability of our airmen, sailors, and marines to attain and sustain the highest levels of military readiness.”

The Obama administration eventually closed the Atlantic to drilling for five years.

Trump could counter Obama’s plan with his own five-year plan, but even so it would be years before drilling could start.

The president-elect’s authority to undo a permanent prohibition is unclear. But Congress, controlled by Republicans, could move to rescind the withdrawal of federal lands from oil and gas exploration.