Back in April, Trump asked Interior Secretary Ryan Zinke to review roughly two dozen national monuments created by Bill Clinton, George W. Bush or Barack Obama.
Leaked documents obtained by The Associated Press show that Trump plans to shrink Bears Ears National Monument by nearly 85 percent and reduce Grand Staircase-Escalante National Monument by almost half.
Trump has pushed to roll back regulations that prevent development.
The Trump administration can resize an existing national monument thanks to a provision in The Antiquities Act of 1906.
Utah Republican leaders had complained that the monuments locked up too much federal land.
Americans from both parties are eagerly waiting for Trump's announcement.
From the maps, it appears Bears Ears, that covers 1.35 million acres, will be eliminated.
Trump's plans to curtail the strict protections on the sites have angered tribes and environmentalist groups who have vowed to sue to preserve the monuments.
Natalie Landreth, an attorney for the Native American Rights Fund, said her group has already drafted a lawsuit to challenge Trump's action, which she called unprecedented and illegal.
Bloch said conservation groups are concerned that Trump's announcement will include an order to offer areas in the monuments for public lease sales for coal mining or oil and gas drilling.
In December, shortly before leaving office, Obama irritated Utah Republicans by creating the Bears Ears National Monument on 1.35 million acres of land sacred to Native Americans and home to tens of thousands of archaeological sites, including ancient cliff dwellings.
Under the Trump plan, Grand Staircase-Escalante, that covers 1.9 million acres, would be reduced to under 1 million acres and split into three new monuments: Grand Staircase, Kaiparowits and Escalante Canyons.
Some Utah county officials welcome a reduction in the size of the monuments, which they say has restricted road access to protected areas. The White House refused comment on Trump's plans.
"We are grateful that somebody is listening to our local voice", he said.