Trump is expected to speak at the Utah State Capitol in Salt Lake City at 12:30 p.m. According to reports, he will announce the gutting of the 1.3 million acre Bears Ears National Monument by 85 percent and the slashing of the 1.9 million acre Grand Staircase-Escalante National Monument by 50 percent. The move will be the largest elimination of protected areas in U.S. history.

National monuments can be designated by presidents under the Antiquities Act, which puts the lands off limits to drilling, mining, logging and ranching. Trump says former presidents abused the act.

Bears Ears was designated in 2016 by President Barack Obama. Grand Staircase-Escalante was created by President Bill Clinton in 1996.

Trump's plan to shrink the two monuments came after a review by Interior Sec. Ryan Zinke that the president ordered in April. Fossil fuel-linked advocates have long targeted the areas for oil, gas and coal resources within and around the monuments' boundaries. According to Zinke's leaked memo, Grand Staircase-Escalante sits atop "several billion tons" of coal. Coal and oil reserves also surround Bears Ears.

Trump's decision was made despite widespread public support of the designations. More than 2.8 million people submitted comments to the Interior Department urging the administration to preserve protections for the lands.

Over the weekend, more than 5,000 people rallied at the Utah State Capitol to protest Trump's decision.

"Flatly, Trump does not have the legal authority to gut our national monuments nor does he have the support of the people of Utah to do so. Thousands of Utahns raised their voices today, in recognition of the cultural, archaeological, and environmental significance of these areas," Sierra Club Utah Chapter Director Ashley Soltysiak said of Saturday's demonstration. "Today's rally showed the strength of support for Tribal sovereignty and Utah's public lands."

A protest is also planned at the State Capitol during the president's visit today.