Joe Biden has banned offshore drilling across an immense area of coastal waters, weeks before Donald Trump takes office pledging to massively increase fossil fuel production.

The US president’s ban encompasses the entire Atlantic coast and eastern Gulf of Mexico, as well as the Pacific coast off California, Oregon and Washington, and a section of the Bering Sea off Alaska.

A White House statement said the declaration protected more than 253m hectares (625m acres) of waters. Trump said he would “unban it immediately” as soon as he re-enters the White House on 20 January, although it is unclear whether he will be able to do this easily.

“As the climate crisis continues to threaten communities across the country and we are transitioning to a clean energy economy, now is the time to protect these coasts for our children and grandchildren,” Biden said in a statement.

“In balancing the many uses and benefits of America’s ocean, it is clear to me that the relatively minimal fossil fuel potential in the areas I am withdrawing do not justify the environmental, public health, and economic risks that would come from new leasing and drilling,” he added.

Scientists are clear that oil and gas production must be radically cut to avoid disastrous climate impacts. The ban does not have an end date and could be legally – and politically – tricky for Trump to overturn.

Biden is taking the action under the Outer Continental Shelf Lands Act of 1953, which gives the federal government authority over the exploitation of offshore resources. A total of eight presidents have withdrawn territory from drilling under the act, including Trump himself who barred oil and gas extraction off the coasts of Florida, Georgia and South Carolina.

However, the law does not expressly provide for presidents to unilaterally reverse a drilling ban without going through Congress.

Despite this, Trump vowed to undo Biden’s move, with the president-elect’s spokesperson, Karoline Leavitt, calling it “a disgraceful decision” and saying the incoming administration would “drill, baby, drill”.

In an interview with the conservative radio host Hugh Hewitt on Monday, Trump said the rule would be overturned on his first day. “I will unban it immediately,” he said. “I have the right to unban it.”

Environmental groups, on the other hand, welcomed the decision. “This is an epic ocean victory!” said Joseph Gordon, climate and energy director at the conservation non-profit Oceana. “Our treasured coastal communities are now safeguarded for future generations.”

“Americans on both sides of the aisle support protecting our oceans from big oil giveaways,” said Lena Moffitt, executive director of Evergreen Action. “President Biden’s bold action today underscores that we cannot afford the continued expansion of oil and gas production if we are to meet our climate targets and avoid the worst impacts of the climate crisis.”

The White House said: “With today’s withdrawals, President Biden has now conserved more than 670m acres of US lands, waters, and ocean – more than any president in history.”

The move is the latest in a string of last-minute climate policy actions by the Biden administration before Trump’s return to the White House.

In mid-December, the outgoing administration issued an ambitious new climate target under the landmark Paris accord, committing the US to reducing economy-wide greenhouse gas emissions by between 61% and 66% below 2005 levels by 2035, on the path to achieving net zero by 2050. Trump is expected to ignore this target, and remove the US from the Paris climate deal.

Biden is also expected to announce two new national monuments – protected lands designated at the discretion of the president – in California before he leaves office. When last in office, Trump shrank the size of two previously established national monuments in Utah.

The outgoing Biden administration has styled itself as as historic leader in environmental policy, passing sweeping legislation to bolster clean energy output and electric vehicle uptake, although the president has also overseen a record boom in oil and gas production and handed out drilling leases at a higher rate even than Trump.

Climate advocates have urged Biden to declare a climate emergency and reverse the growing export of gas from US-based shipping terminals before Trump’s new term.

Agence France-Presse contributed reporting