Within minutes of being introduced as the new secretary of defense Friday, John Tower indicated he intends to make a dramatic change in the way the Pentagon does business.

Tower, twice passed over for the job by Reagan, has been in lonely encampment in a Washington hotel suite for three weeks awaiting a final decision by President-elect George Bush and has had plenty of time to think about how to manage the Pentagon.Asked Friday about the dangerously top-heavy Pentagon budget, Tower suggested he will reverse the current process of setting a dollar figure for defense spending and fitting as many programs as possible under that lid.

Instead, Tower said, he - together with military and congressional leaders and other members of the Bush administration's national security team - will start by defining U.S. national security objectives, and then examine how the military supports those objectives.

Only when that process of "rationalizing" the armed forces is completed, Tower said, will he be ready to propose specific reductions and realignments in defense spending.

His implication - that he intends to hold the Defense Department brass to a new standard of strategic accountability - may have struck fear into jealous Pentagon guardians of cherished but anachronistic programs.

But the diminutive and dapper Texan left no doubt he means to do that.

"We must provide at least as much, if not more, defenses for less money," he said at a news conference with Bush. The job will be "difficult and challenging," he said.

Tower suggested he may delay a critical decision on whether to deploy mobile MX or Midgetman strategic missiles.

He also endorsed the controversial strategic missile defense program, saying "Star Wars" weapons should be deployed "as soon as (is) feasible." But he pointedly did not endorse the "early-deployment" option for space-based defenses that many conservatives favor.

Tower's first job, however, will be dispelling some of the skepticism that his selection has engendered in the Pentagon and on Capitol Hill.

"These are the right words, but I'm doubtful he'll actually follow through with changes," said Steve Daggett, a defense budget analyst at the liberal Committee for National Security. "There's still a tendency to underestimate how bad the budget crunch is, and therefore not to be as vigorous in rethinking priorities."

Indeed, the military service chiefs and other senior officers already have launched pre-emptive strikes against pending budget cuts.

Adm. William J. Crowe, chairman of the Joint Chiefs of Staff, said in an interview with Reuters, "The professional military is opposing these cuts."

Gen. Alfred M. Gray Jr., commandant of the Marine Corps, warned against "repeating the costly mistake of the 1970s" when personnel and operating costs were deeply cut.

And Gen. Joseph Palastra, commander of the Army Forces Command, cautioned that his service's assets are already "not sufficient to execute with a high degree of confidence all of the Army contingency plans at the same time."

Attacking from a different direction, congressional critics said Tower may not cut deeply or ruthlessly enough, judging by his record as an uncritical champion of higher defense spending while he was chairman of the Senate Armed Services Committee during Reagan's first term, and his coziness with defense contractors as a consultant in the years following his retirement from the Senate in 1985.

Rep. Les Aspin, D-Wis., chairman of the House Armed Services Committee, called the choice "the first serious misstep" of the Bush administration.

With Tower's record of opposing Pentagon reforms, congressional concern over his appointment "is pretty deep," said Sen. Charles Grassley, R-Iowa.