US President Donald Trump has signed an executive order to identify national monuments that can be rescinded or resized - part of a broader push to open up more federal lands to drilling, mining and other development.
The move comes as part of Trump's effort to reverse a slew of environmental protections ushered in by his predecessor, Democratic President Barack Obama, that he said were hobbling economic growth, an agenda that is cheering industry but enraging conservationists.
The Republican president signed the order at the Interior Department in Washington, saying that Obama's use of the 1906 Antiquities Act to create monuments marked an "egregious abuse of federal power" allowing the federal government to "lock up" millions of acres of land and water.
"Today we're putting the states back in charge," Trump said, saying they should decide what areas of land should be protected.
The monuments covered by the review will range from the Grand Staircase created by President Bill Clinton in 1996 to the Bears Ears created by Obama in December 2016, both in Utah.
Interior Secretary Ryan Zinke told reporters late on Tuesday that Trump's order would require him to conduct the review of around 30 national monuments created over the past two decades, and recommend which designations should be lifted or altered.
Zinke said he would seek local feedback before making his recommendations, and added that any move by Trump to ultimately reverse a monument designation could be tricky.
Legal challenges are expected because no president has ever rescinded a monument designation.
The Bears Ears area lies near where Texas-based EOG Resources Inc had been approved to drill.
Republican House of Representatives Speaker Paul Ryan praised the order.
"I commend the Trump administration for stopping this cycle of executive abuse and beginning a review of past designations," he said.
Conservation and tribal groups criticised the order.
"With this review, the Trump Administration is walking into a legal, political and moral minefield," said Kate Kelly, public lands director for the Center for American Progress.
Democratic Congressman Raul Grijalva of Arizona, ranking member of the House natural resources committee, warned Zinke not to make an "ideological" decision, adding that previous monuments were done "after years of close federal consultation with multiple local stakeholders."
The Outdoor Industry Association, the trade group of the recreation industry, also attacked the order.
