By Valerie Volcovici

WASHINGTON (Reuters) - President Barack Obama on Wednesday designated over 1.6 million acres of land in Utah and Nevada as national monuments, protecting two areas rich in Native American artifacts from mining, oil and gas drilling in one of his final moves to protect the environment.

"Today’s actions will help protect this cultural legacy and will ensure that future generations are able to enjoy and appreciate these scenic and historic landscapes," Obama said in a statement.

Obama used the 1906 Antiquities Act to protect 1.35 million acres of federal land at Bears Ears in Utah and 300,000 acres at Gold Butte outside of Las Vegas, Nevada. The move will be difficult for President-elect Donald Trump to reverse.

Utah's governor and congressional delegation opposed the designation as a national monument, saying it went against the wishes of Utah citizens.

"I am deeply disturbed by what has resulted from a troubling process," Utah Governor Gary Herbert said in a statement. "The president has misused his authority." He said the state will "aggressively" challenge the action through administrative, legal and legislative means.

Nevada Governor Brian Sandoval said he would have preferred a more collaborative approach involving the state's Congressional delegation, ranchers, environmentalists and community members. However, he recognized the "inevitability" of the designation and worked with federal officials on the proposed boundary and to ensure state water laws were followed.

“My priority was to mitigate any disruption a potential designation may cause the surrounding private land owners, communities and recreationists," he said in a statement.

Obama has used the Antiquities Act and other measures to protect more land and water than any administration in history, the White House said in a statement.

Various tribes and lawmakers have been trying for years to protect the Bears Ears region, home to a wealth of Native American sacred sites, rock art, ancient cliff dwellings and other areas of cultural significance.

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Bears Ears has been home to Hopi, Navajo, Ute Indian Tribe, Ute Mountain Ute and Zuni, whose leaders welcomed the announcement. The designation will allow them continued access to tribal ceremonies, firewood and herb collection, hunting, grazing and outdoor recreation.

“As a coalition of five sovereign Native American tribes in the region, we are confident that today’s announcement of collaborative management will protect a cultural landscape that we have known since time immemorial,” said Alfred Lomahquahu, vice chairman of Hopi Tribe.

Lomahquahu will serve as a co-chair of the new Bears Ears Inter-Tribal Coalition, which will administer the use of the land with federal and state government partners.

Gold Butte in Nevada is home to both Indian artifacts and American pioneer sites.

"The splendor of Gold Butte will now be protected for all of us. It will be enjoyed for generations to come," said Nevada Democratic Senator Harry Reid.

U.S. Representatives Rob Bishop and Jason Chaffetz, both Republicans, had proposed a land-use bill called the Public Lands Initiative that would have created two national conservation areas for some of Bears Ears but enabled development on other areas.

The House of Representatives did not vote on the bill before recess.

Chaffetz on Wednesday called the designation a "midnight monument," accusing Obama of a last-minute designation that "cherry picked" parts of his bill "and disregarded the economic development and multi-use provisions necessary for a balanced compromise."

"We will work to repeal this top-down decision and replace it with one that garners local support and creates a balanced, win-win solution,” he said.

(Reporting by Valerie Volcovici, additional reporting by Ben Klayman in Detroit and Jim Christie in San Francisco; Editing by Leslie Adler and David Gregorio)