WASHINGTON (Reuters) - U.S. Interior Secretary Ryan Zinke said on Monday he has recommended that President Donald Trump reduce the size of the Bears Ears National Monument in Utah - a move that drew quick fire from conservationists but was supported by mining and drilling interests.

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The 1.35 million acre (5,463 square kms) area, designated by former President Barack Obama during his final days in office and named for its iconic twin buttes, is the first of 27 national monuments to be reviewed by the Trump administration as part of a plan to increase development on federal lands.

“My job is to make sure that I ... reflect the concerns of Utah, and reflect the concerns of the taxpayers and the public who own the lands, and I think we’ve done that,” Zinke told reporters in a teleconference about his interim recommendation sent to Trump on Saturday. Zinke toured Utah for four days before making the recommendation.

His report said that the Antiquities Act, used by past presidents to declare monuments, should cover the “smallest area compatible” with protecting important sites.

“Therefore... the Secretary of the Interior recommends that the existing boundary of the (Bears Ears) be modified to be consistent with the intent of the act.”

Rather than designating a vast monument, as Obama did, “it would have been more appropriate to identify and separate the areas that have significant objects to be protected to meet the purposes of the Act,” Zinke’s report said.

More study is necessary to determine how much smaller Bears Ears should be, Zinke said, and that decision will not be made until all of the 27 monuments are reviewed.

Jamie Williams, president of The Wilderness Society, said Zinke’s recommendation was “nothing less than an attack on the future of all American monuments, parks and public lands,” and was “against the wishes of the overwhelming majority of Americans.”

A public comment period that closed in late May generated hundreds of thousands of comments, with the majority expressing hope that monuments like Bears Ears remain protected.

Zinke also recommended that tribes be allowed to co-manage “cultural areas” within the resized monument - a nod to Native Americans who had lobbied for protections for the territory - and that Congress review conservation policies in the area.

His recommendation to Trump set the tone for the administration’s broader review, triggered by an executive order in April.

Trump had argued that previous administrations “abused” their right to designate monuments under the Antiquities Act of 1906 and put millions of acres of land, mainly in western states, off limits to drilling, mining, logging and ranching without adequate input from locals.

The review is likely to add fuel to a heated national debate over Washington’s role in America’s wildest spaces. Environmentalists and tribal groups support federal oversight, but many state political leaders, conservatives and industry groups say the lands should generate money for business, creating jobs, or yielding revenue for education and other public services.

While the land encompassed by the Bears Ears monument is not believed to contain huge amounts of coal, oil or gas, several other monuments on Zinke’s review list do - making the Bears Ears decision symbolically important to industry groups.

Kathleen Sgamma, president of the Western Energy Alliance, representing oil and gas companies, said Zinke’s approach was sensible. “It’s clear that Bears Ears was an overreach, and was much larger than necessary to protect cultural resources.”