JUDITH GAP, Mont. — Here in America’s nuclear heartland, where underground missile silos dot the landscape, a proposed U.S.-Russia treaty to reduce nuclear weapons is nothing short of alarming.

The military workers who maintain those missiles support cities as large as Great Falls, where 40 percent of the economy depends upon Malmstrom Air Force Base, and businesses as small as the Judith Gap Mercantile, where passing airmen buy milkshakes by the dozen. If they follow the missiles out of town, the economies here could be crippled.

The fate of the 450 intercontinental ballistic missiles around Malmstrom, F.E. Warren Air Force Base near Cheyenne, Wyo., and Minot Air Force Base in North Dakota is not yet clear, but politicians and community leaders are ready to fight to keep them. Even if it means not cutting nuclear weapons.

“I would keep Malmstrom at full strength, regardless,” Great Falls Mayor Michael Winters said. “Each and every facet of our economy has something to do with Malmstrom.”

Montana, North Dakota and Wyoming business leaders over the past year have lobbied their congressional delegations, all the while avoiding arguments about whose base is more important, said Dale Steenbergen, president of the Greater Cheyenne Chamber of Commerce.

Instead, they’re trying to convince Congress to keep the ICBM silos at full strength, saying they are relatively cheap to maintain and are more secure compared to bombers and submarines that also carry nuclear arms.

“You can sink a sub or shoot down a plane. That’s very different from attacking American soil, and that’s what you’d have to do (to get to the ICBM silos),” Steenbergen said.

The proposed treaty would require the U.S. and Russia to reduce their nuclear warheads over seven years by 30 percent, to 1,550 from a previous maximum of 2,200. But it doesn’t say where those cuts would come.

That’s expected to be detailed in the Defense Department’s Nuclear Posture Review, a comprehensive strategic review of the U.S. nuclear force. The review could be released as early as this week, Pentagon spokesman Cmdr. Bob Mehal said.

Officials at the Air Force Global Strike Command, which oversees the nation’s nuclear-equipped bombers and intercontinental ballistic missiles, declined to comment.

Obama and Russian President Dmitry Medvedev are expected to sign the treaty Thursday. It must then be ratified by two-thirds of the Senate, where critics are directing their lobbying.

Sen. Max Baucus, a Montana Democrat, said he is inclined to support ratification and that the reduction of nuclear warheads is an admirable goal. ICBMs like those at Malmstrom are likely to be spared deep cuts because they are cost-effective and could eventually be converted to carry conventional warheads, he said.

Malmstrom’s 341st Missile Wing employs about 4,000 military personnel and civilians to manage its 150 ICBMs. One maintenance duty is to extend the life of aging Minuteman III missiles, and the Air Force has committed nearly $6.2 billion to such programs, according to Malmstrom’s Web site.

Quantifying the three bases’ economic contribution to their surrounding communities is difficult, but their importance to those cities and towns is clear.

The bases employ thousands and provide contract work for local businesses, and base personnel spend money and pay taxes to the towns. There also is fierce community pride at being at the center of the nation’s defense.

Airmen who service and maintain the missiles pass daily through Judith Gap, a town of about 150 in the center of Montana. Residents are used to regular emergency drills that involve lines of Humvees, helicopters overhead and soldiers with rifles at the ready.

The Judith Gap Mercantile, which says its milkshakes are famous worldwide, takes pride in serving the service members who make up an estimated 70 percent of its business.

“They like to play a little game with us,” said Jancy Kowalski, who makes the milkshakes. “They’ll come in and say, ‘We need 15 milkshakes,’ and we’ve got like 10 minutes to close. They love to do that to us.”

Neither she nor the few patrons in the store Tuesday would speculate on what losing the military trade would do, but a longtime resident said it would devastate a farming and ranching community already hurt by recession.

“You’ll find more people going out of business, selling their farms,” Andrew Arneson said.

Grand Forks, N.D., lost its 150 ICBMs to Malmstrom in a 1995 Base Realignment and Closure round.

City Councilman Eliot Glassheim said Grand Forks hired lobbyists and spent hundreds of thousands of dollars to fight the closure, but to no avail. The city fell from second to third in the state in population and economy, Glassheim said.

Grand Forks Air Force Base now supports unmanned aerial vehicles, but the city has diversified its economy so that it’s not as reliant upon the military.

Steenbergen said he believes the three states can maintain their nuclear manpower and number of operating silos — which can house more than one missile — but may see fewer missiles because of the cuts. “Some folks are getting nervous, but I think they’re leaping to some conclusions,” he said.