President Donald Trump has signed an executive order requiring a review of environmental protections given to lands owned by the federal government.
The order aims to shrink the borders of national monuments created by previous presidents, which Mr Trump called an "egregious abuse of federal power".
Unlike national parks, which require an act of Congress, national monuments can be created by a presidential directive.
However, a president does not currently have the right to abolish a monument.
The White House intends to shrink the borders of existing national monuments that have drawn controversy from Republican lawmakers and the mining industry.
Environmentalists fear this order will unleash a wave of new oil and gas extraction, which was a Trump campaign promise.
It directs the Department of Interior to examine all lands designated as national monuments since 1996.
The 1.35 million acre Bears Ears National Monument in Utah, created by Barack Obama during the final days of his administration, is one of the parks under review.
Utah lawmakers oppose the Obama action and have lobbied Mr Trump since his November election to overturn it.
Mr Obama placed 553 million acres under national monument protection during his presidency - more than any other US president.
This, his successor said, was an abuse of the law which eliminated the ability of people in these states to decide how best to use the land.
Rob Bishop, chairman of the House Committee on Natural Resources, said: "I'm pleased to see President Trump recognise long-standing abuses of the Antiquities Act.
"It was created with noble intent and for limited purposes, but has been hijacked to set aside increasingly large and restricted areas of land without public input."
Environmental groups panned Mr Trump's latest action to undo his predecessor's environmental legacy.
"An attack on one national monument is an attack on all," said Theresa Pierno of the National Parks Conservation Association.
"These public lands are owned by all Americans. Communities are doing their job to protect them. Our elected officials must do the same."