At a time when the Pentagon is shutting down dozens of bases worldwide and bracing to pull thousands of troops out of central Europe, the Air Force is preparing to break ground on a sprawling new $727 million NATO air base in the dusty farmlands of southern Italy.

The Crotone air base -- with hangars and runways for 72 F-16 fighter jets and housing and a shopping mall for hundreds of military families -- has become a controversial symbol of the military and political struggles to reshape the armed forces in an age of budget cuts and easing tensions between the superpowers.

Top military officials are plugging the facility as a "21st century air base" critical to the defense needs of southern Europe now that the Spanish government has refused to renew the lease on the NATO fighter base in that country. Some members of Congress have dubbed it a NATO boondoggle: "Our little Italian theme park," chided one member.

Just as U.S. military officials had finished negotiating one of the most favorable NATO base deals in history -- allies agreed to pick up the tab for more than half of the $727 million base costs -- world events and domestic budget problems have conspired to sabotage the agreement.

"I see absolutely no reason for this base," said Rep. Patricia Schroeder (D-Colo.), head of the military construction panel of the House Armed Services Committee and author of legislation barring the United States from spending any money on the Crotone air field. "When we're closing 86 bases in the United States and building a new base in an area where the threat is severely lessened, people are asking, 'What's going on?' "

Congress last year capped the U.S. contribution to the Crotone base construction and other costs involved in moving out of Spain at $360 million.

Top military and civilian officials based in Europe have begun a vigorous lobbying campaign on Capitol Hill to blunt growing opposition to U.S. funding for the base.

"I am fully aware that asking for money now to build a new base in Europe is particularly disagreeable," Gen. John R. Galvin, chief of the allied forces in Europe, told the Senate Appropriations Committee's defense panel last week. "I consider Crotone the legitimate price we must pay to maintain peace and stability in southern Europe. . . . "

Pentagon officials argue that expected troop cuts in central Europe only bolster the need for the fighter wing in the southern region. In a secret report to Congress, the Defense Department warned: "Recent analysis taking into account the ongoing changes in the European security environment have reconfirmed the absolutely critical need of an in-place wing of F-16s in the southern flank of NATO. From a military perspective, the 401st Tactical Fighter Wing is irreplaceable." Military officials say the Italy-based planes would protect Greece and Turkey from attack.

"Who are we defending the southern flank from?" asked Sen. Jim Sasser (D-Tenn.), chairman of the Senate Appropriations Committee's military construction subcommittee. He said he plans to propose legislation that would allow the United States to contribute about $50 million to a scaled-down, "bare bones" base.

Military officials say privately that the base also would provide well-placed air power to counter problems in the Middle East. The planes, for example, are close enough to Libya to conduct a mission without refueling, officials said. That is a sensitive aspect of the base, which the Italian government is hesitant to publicize for fear of antagonizing Libya and Middle Eastern nations.

The battle over the Crotone base began two years ago when the Spanish government ordered NATO and U.S. Air Force planes out of the large Torrejon Air Force Base. U.S. officials, citing budget problems even then, responded by saying it would relocate the 401st Tactical Fighter Wing in the United States.

That brought protests from NATO allies and an offer from Italy to accept the planes. But Italy was picky about the location. It rejected a site selected by an Air Force search team and insisted that the base be constructed near isolated, economically depressed Crotone (pronounced Cro-TOE-nee) in the arch of the boot of southern Italy.

The location further antagonized U.S. officials when local farmers demanded $12,000 an acre for their arid farmland, far more than American officials believed the land was worth.

"It's become more of an economic development project for southern Italy," complained Schroeder. "As we close bases in the United States, economic development is not allowed as an excuse to keep a base open."

And there are still other problems that have little to do with congressional politics or a weakened Soviet threat:

The Crotone base won't be finished until at least three years after the 401st leaves Spain in 1992, forcing the United States to consider temporary relocations in West Germany, northern Italy and the United States.

U.S. and Italian officials have been unable to reach an agreement on a training/bombing range near the planned Crotone facility. If the Italian government doesn't offer adequate training space, the fighter planes would be forced to fly to Turkey for training missions.

A University of Texas archaeological team has complained that the planned construction could destroy relics from the 7th century B.C. that lie beneath the planned base.

The U.S. costs for relocating the fighter wing from Spain extend beyond the $262 million it is contributing for the construction of Crotone. American taxpayers are scheduled to finance another $100 million in costs associated with moving other units out of Spain, severance pay for Spanish civilian employees who had worked at the base and environmental cleanup projects.

"We're getting a helluva bargain" with Crotone, Air Force Chief of Staff Gen. Larry D. Welch told a group of reporters last week.