By Debbie Hummel

SALT LAKE CITY (Reuters) - The state of Utah, long resentful that some 60 percent of its territory belongs to the U.S. government, says the time has come to reclaim the millions of acres it gave up more than a century ago for admission to the union.

Governor Gary Herbert signed into law on Friday a bill demanding the federal government relinquish ownership of roughly 30 million acres of public land in Utah by 2015 or face a state lawsuit challenging its continued control of that property.

Shrugging off warnings from state attorneys that the legislation, backed primarily by Republicans, is likely unconstitutional and could lead to a protracted but futile legal battle, Herbert called such a dispute "a fight worth having."

The measure, opposed by conservation groups, caps years of rising indignation in Utah's conservative political establishment over the fact that about 65 percent of the state's land mass is owned by various federal agencies, the bulk of it by the Interior Department's Bureau of Land Management.

Critics have complained that federal control over vast tracts of Utah's territory has put too much land off-limits to commercial activities, such as energy development, limiting the state's tax base for schools and other public services.

"The director of BLM has more control over our state than the governor," Herbert, a first-term Republican, said at a news conference following a bill-signing ceremony at the state capitol in Salt Lake City.

"The federal government retaining control of two-thirds of our land mass was never in the bargain when we became a state, and it is indefensible 116 years later," Herbert added in a statement issued by his office.

Herbert and other supporters have focused especially on the potential for greater funding for education in Utah, which ranks near the bottom in per capita expenditures for public school students among the 50 states.

COULD AFFECT NATIONAL RECREATION SITES

The new law calls on the federal government to transfer title to properties held by the BLM, U.S. Forest Service and other agencies to a Utah public lands commission by January 1, 2015. The state's five national parks, its military installations and some federal wilderness areas are exempt.

But the measure would likely affect such sites as the 1.9-million-acre Grand Staircase-Escalante National Monument, the Glen Canyon National Recreation Area and other national recreation sites and wildlife refuges, said Steve Bloch, conservation director for the Southern Utah Wilderness Alliance.

Debate over Utah's federal holdings has flared several times since statehood was granted in 1896, but supporters of the newly enacted measure point to recent federal court decisions that they say bolster their case for reclaiming public lands.

Their claims are based in part on an interpretation of Utah's century-old enabling act under which they say Congress promised to return federal lands after statehood. Proponents argue that Congress reneged on that promise in a 1970s statute that retained federal land ownership in Utah but pledged greater state control and access as an alternative.

Foes of the measure say its supporters are misreading Utah's founding documents and that there is no legal basis for the state to unilaterally claim ownership of federal lands.

That has not stopped lawmakers in other big Western states with large federal landholdings, such as Arizona, from pushing for similar measures.

Utah state Representative Ken Ivory, the chief sponsor of Friday's bill, said a similar measure has already passed the Arizona state House of Representatives and is awaiting a hearing in the state Senate.

(Additional reporting by Jennifer Dobner and Bob Bernick. Writing by Steve Gorman; Editing by Cynthia Johnston)