Zinke told reporters Tuesday he is "fairly confident" Trump will accept his recommendations.
The reasoning behind the move is to designate as protected "the smallest area compatible with the protection of the objects of scientific or historic interest", and the proclamation also opens the newly public lands to "disposition under all laws relating to mineral and geothermal leasing; and location, entry, and patent under the mining laws".
"The Antiquities Act was created to protect rather than prevent, and no president, under the authority of the Antiquities Act, has the authority to arbitrarily remove the public from their lands, reduce public access, reduce hunting and fishing and reduce traditional uses, unless those uses threaten the object", Zinke said. "Public lands will once again be for public use, because we know that people who are free to use their land and enjoy their land are the people most determined to conserve their land", he said.
"It's an attack on all of our National Monuments, an attack on one in an attack on all, so we want to come out here and stand in solidarity of protection of our national treasures", Gabriel Otoro, organizer of the rally, said.
According to a lawsuit, obtained by TMZ, Trump's controversial decision to strip 900,000 acres from Grand Staircase-Escalante National Monument is an attempt to reverse President Clinton's 1996 decision to create the Monument. "The Bears Ears region is a cultural landscape - a place to nurture our families in our traditions". The last president to use his power to reduce the size of a monument was John F. Kennedy in 1963.
Both monuments span millions of acres in Utah and are among 27 national monuments that Trump ordered his Interior Secretary to review earlier this year.
Unlike national parks, which are established by Congress, the Antiquities Act allows national monuments to be designated either by Congress or the president.
Utah's Republican leaders pressed Trump to launch the review, saying the monuments declared by Presidents Barack Obama and Bill Clinton locked up too much federal land.
At least five Native American tribes announced they'll sue the president over the reduction of Bears Ears, a monument they consider sacred and important to their culture. The plans would break Bears Ears into two national monuments and Grand Staircase-Escalante into three separate monuments.
"More than 150 years ago, the federal government removed our ancestors from Bears Ears at gunpoint and sent them on the Long Walk", Navajo Nation Council Delegate Davis Filfred said in statement. The President's move was met with protests in Utah and in San Francisco by environmentalists and some Native Americans.