President Donald Trump has signed proclamations to formally scale back two sprawling national monuments in Utah: Bears Ears and Grand-Staircase Escalante.

Trump traveled to Salt Lake City to make the announcement and sign the declarations. The move is supported by Utah's top Republican officials but opposed by tribes and environmental groups.

Trump said in a speech Monday at the Utah State Capitol that past presidential administrations had "severely abused" the purpose and spirit of a federal law that allows them to protect public lands by turning them into national monuments.

Trump says his action means that "public lands will once again be for public use."

The Trump administration plans to cut Bears Ears by 85% Grand Staircase by 50%. 

The two national monuments were among 27 that Trump ordered Interior Secretary Ryan Zinke to review earlier this year.

Trump signed an executive order in April directing Zinke to conduct a review of the protections. Trump is able to upend the protections under the 1906 Antiquities Act, which gives the president broad authority to declare federal lands as monuments and restrict their use.

During a speech, he said, "Utah's awesome natural beauty is exceeded only by the warmth and grace and hospitality of its citizens."

The president also promised the protect the people's religious liberty.

"Some people think that the natural resources of Utah should be controlled by a small handful of very distant bureaucrats, and guess what? They're wrong," Trump said.

Zinke also has recommended that Nevada's Gold Butte and Oregon's Cascade-Siskiyou monuments be reduced in size, although details remain unclear. The former Montana congressman's plan would allow logging at a newly designated monument in Maine and more grazing, hunting and fishing at two sites in New Mexico.

Trump previously had condemned the act of creating the Utah monuments as a "massive federal land grab."

Both monuments were created by Democratic Presidents Barack Obama and Bill Clinton.

Chris Saeger, executive director of the Western Values Project, released the following statement:

"This decision is a dangerous turn in our nation’s approach to protecting the places that have forged the Western way of life. The fact that an American president would unlawfully remove protections on iconic public lands for political gain should deeply disturb anyone who wants these places, which are a birthright to our children, to continue to benefit all of us."

“For his part, Secretary Zinke should be ashamed of his role in this craven decision to allow special interests to exploit the kinds of places President Roosevelt signed the Antiquities Act to protect. Fortunately, legal experts overwhelmingly agree that undoing these protections is unlawful and will not stand.”

“Future generations are counting on our system of checks and balances to stand up to this shocking abuse of power."

The following statement is from Jamie Williams, president of The Wilderness Society: 

“The Trump administration has declared 'open season' on places Americans hold dear so that profit-seekers can drill, mine and log our public lands for private gain. By making commercial exploitation of these national treasures the top priority, this administration betrays the history of these sacred places, as well as their value as places for people to enjoy the outdoors and for wildlife to thrive.
The Trump Administration has callously ignored the millions of Americans who have spoken out in support for our national monuments.  With this radical approach to managing our national treasures, none of the nation’s natural and cultural wonders are safe from this administration’s agenda. 
Any action by the Administration to erase or permanently damage these national monuments is not only illegal but also an insult to the owners of this land – the American people – and will be challenged by The Wilderness Society in court.

(The Associated Press, CBS News contributed to this report.)