Tonight I hear the neighborhood drummer sound
I can feel my heart begin to pound
You say you're tired and you just want to close your eyes
And follow your dreams down.
— Bruce Springsteen

LAS VEGAS — As "No Surrender," Bruce Springsteen's anthem of defiance, blared inside the convention center of the MGM Grand hotel last Tuesday, Ron Gettelfinger, the president of the United Automobile Workers union, locked arms with the union's other leaders and led hundreds of delegates in a rousing march peppered with blue-and-gold protest signs.

The march was an impressive display of bravado, calling to mind the heady days of the late 1940's when the U.A.W.'s legendary leader, Walter Reuther, assumed the union's helm after directing years of strikes and canny organizational maneuvers against industry giants like General Motors and Ford. And the whoops, cheers and lyrics ("No retreat, baby, no surrender") here made it seem that current union members were again ready to take on the auto companies anywhere, anytime.

But the signs that the delegates toted served only to reveal the tension and uncertainty that the boisterous demonstration was meant to conceal. "Don't Agonize, Organize!" declared one sign, reflecting the fact that the union's membership, once 1.5 million strong, is now just one-third that size, its lowest number since World War II. "Protect Our Pensions," read another placard, recognizing the threat to union nest eggs at troubled companies. Another sign, "Active and Retired, Standing Together" gestured toward the reality that the U.A.W.'s dwindling active membership would soon be outnumbered by members earning retirement checks.

So it is that Mr. Gettelfinger, 61, elected last week to a second and final four-year term as U.A.W. president, is forced to rally his members when the auto industry is mired in declining profits and tethered to a very uncertain future. And as his union confronts its most crucial economic juncture in decades, the question arises of what, exactly, he plans to do to ensure that the U.A.W. retains its influence and protects its members.

Mr. Gettelfinger's short answer is twofold: he plans to step up the union's organizing drive, which in the past has not been enough to offset steep job losses at the auto companies, and to wield its political clout for broader changes in Washington. Neither, however, addresses the union's true quandary.

"He has an extremely difficult set of circumstances facing his members," said Bruce S. Raynor, general president of Unite Here, a union that represents hotel and other service workers. "He is trying to walk a fine line. He is trying to safeguard what the U.A.W. has obtained for its members and he has to be intelligent and not to deny reality."

Like his members, Mr. Gettelfinger seems determined to prove wrong those who dare to count out the brawny U.A.W. of old. At the same time, he has signaled that the past cannot be a template for the future. His statements about possible solutions for the union are code, some industry analysts say, for wage and benefit cuts. Mr. Gettelfinger denies that this is what he means, and he has left an equally strong impression among U.A.W. members, analysts and auto executives that he is cut from Reutherian steel and would authorize a potentially crippling strike if it protected jobs.

WHILE toeing this delicate line between flexibility and resolve, Mr. Gettelfinger addressed the current state of uncertainty here in a thundering speech, delivered in his southern Indiana twang. The powerful address reminded his audience of one of the reasons that he ascended to the U.A.W.'s top job: he knows how to motivate the membership.

"They think we've run out of gas intellectually and emotionally, that we've lost our will, our creativity and our nerve," he said, before pounding on the lectern amid cheers. "We've got news for them. We're not going to surrender. We're not going to lower our sights, give up our dreams or give up our fight for a better world for our children and grandchildren."

The U.A.W., long the envy of the labor movement for its rich contracts and reputation for promoting large social and political changes, has a history of being adept at cagey, strategic confrontations.

One such moment came in 1946, when Detroit began converting plants back to auto production after using them to build bombers and weaponry during World War II. Even though Americans were hungry for new cars, Mr. Reuther staged a 113-day strike at G.M. when the company refused the U.A.W.'s demand for a wage increase of 1 cent more an hour. Ultimately, the union got its way.

The union won another key demand — full retirement benefits after 30 years on the job — after a 67-day strike at G.M. in 1970. The U.A.W.'s last major walkout occurred in 1998, when a strike in two plants in Flint, Mich., shut down much of G.M.

But strikes on a national scale today have the potential to be much more explosive, given the auto industry's perilous state. If the union struck now, it could send G.M. into bankruptcy alongside the Delphi Corporation, its biggest parts supplier and a former subsidiary. In the process, the strike could also wipe out thousands of jobs on top of the 30,000 that G.M. already intends to cut under a restructuring plan.

So a strike, the greatest weapon the U.A.W. can wield, holds the potential to cripple the union itself — thereby undermining its goal of job creation.

But Mr. Gettelfinger has also shown a flexible side. Under his leadership, the U.A.W. has reached agreements with G.M. and Ford that reduced prized benefits like health care, and a pact with Chrysler that eliminated some of the elaborate work practices the union had long insisted were needed to protect jobs.

"He is so centered in what he considers to be right and wrong that nobody, not the company or others, can shake him in that conviction," said Joe W. Laymon, the executive vice president for human resources and labor relations at Ford.

Others, particularly workers themselves, say they think that Mr. Gettelfinger bends so far that he is in danger of appearing malleable.

"The only gains we've ever made at the bargaining table came through withholding our labor," said Brian Kerr, who has spent 29 years at Caterpillar, where the U.A.W. had two long strikes and he walked a picket line two nights a week for years. "Words are words; actions are actions."

The U.A.W. oversees a contract the size of the Manhattan phone book, and it has spent years trying to protect its prerogatives. One of the most treasured was fully paid health coverage for active and retired workers, considered one of Mr. Reuther's landmark accomplishments when it was achieved in the early 1960's. Despite union members' long-held belief that health care coverage was sacred, Mr. Gettelfinger agreed last fall to plans at G.M. and Ford that required workers to pay for part of their coverage. Some 60 percent of the workers at G.M., which lost $10.6 billion last year, accepted the plan.

But workers barely approved the plan at Ford, shocking union officials. Perhaps because of that — and because Mr. Gettelfinger has been so busy negotiating a deal to avoid deep cuts at Delphi — a similar health care agreement has yet to be reached at Chrysler. Bill Parker, president of a U.A.W. local at Chrysler, predicted that workers would vote down such a pact.

Although Mr. Parker does not oppose Mr. Gettelfinger's efforts to help the weaker car companies, he questioned whether the same strategy was appropriate for Chrysler, which was profitable last year. "Are we facing reality?" he asked. "The situation at Chrysler is substantially different than the situation at G.M. and Ford."

It was one thing for the U.A.W. to grant concessions to Chrysler in 1979, when the givebacks were a crucial part of clinching a federal bailout, Mr. Parker said. But he sees no need now to accept health care cuts.

On Thursday, Mr. Gettelfinger refused to discuss the negotiations between the U.A.W. and Chrysler.

BUT the union's relationship with Chrysler provides valuable clues to what the union's overall strategy with the major auto companies may look like in coming years.

Outside Dundee, Mich., 60 miles south of Detroit, is the Global Engine Manufacturing Alliance plant, or GEMA, a venture of Chrysler, Mitsubishi of Japan and Hyundai of South Korea.

Working under a streamlined contract the size of a pocket datebook, U.A.W. members there have just one job classification, versus the dozens found at more typical plants. Each worker has the training for a variety of jobs, in contrast to workers at traditional factories, who might toil at one task, like assembling instrument panels, for years on end.

"You can see Ron's willingness to take creative approaches to try to deal with complex issues," said John S. Franciosi, the senior vice president for labor relations at Chrysler.

Indeed, the U.A.W. is willing to do such things if they will help guarantee jobs, said James Pedersen, one of Mr. Gettelfinger's political affairs directors. "Our concerns are our jobs," he said. "The question is, does our message get out, or the message of our adversaries?"

Such uncertainties were heightened last fall after Delphi outmaneuvered the U.A.W. by filing for bankruptcy protection. Delphi's chief executive, Robert S. Miller Jr., went almost unchallenged in his attacks on U.A.W. wage and benefit rates and drew a wide audience for his insistence on deep cuts. Mr. Gettelfinger chose to reply to the critiques primarily in a press release, and the U.A.W. offered a more robust response only after workers at plants in Michigan and Ohio began protesting against any cuts.

Ultimately, the U.A.W. joined with five other unions at Delphi to fight the cuts, which have yet to be imposed. Delphi has filed a motion in federal court seeking to void its current labor contracts, but the hearing has been postponed until August to give Delphi and the unions an opportunity to reach a settlement.

Despite Mr. Miller's threats, workers are still earning the same wages they did when Delphi sought bankruptcy protection — and will for at least a few more months. The union's tactics, Mr. Gettelfinger said, had put the U.A.W. in a position "where we were able to hold our own."

In the meantime, Delphi, the U.A.W. and G.M. negotiated buyouts and retirement incentives that would allow Delphi workers to retire or leave with their pensions and, for some, their health care plans intact.

Retired union members, who are on the verge of outnumbering active workers, prize those benefits, and their influence within the U.A.W. has never been greater. While retirees cannot vote on U.A.W. contracts, they vote in local elections, serve as convention delegates and pay voluntary dues of $2 a month. They are also fiercely loyal.

"The U.A.W. changed the culture for people in the world; it really did," said Clarice Squillace, a retired G.M. worker from Detroit. But Ms. Squillace said she would be happy if Mr. Gettelfinger could recruit enough new members to tip the balance in the other direction.

Yet organizing has been one of the union's biggest failings in the last quarter-century. Despite years of U.A.W. recruitment efforts, there are now 60,000 non-union workers at foreign-owned domestic plants, and that figure is likely to grow substantially as more foreign-owned plants come on line.

BOB KING, a U.A.W. vice president who has overseen recruitment drives, says the union is changing tactics and will focus on new Hyundai and Nissan plants because they pay considerably lower wages than the other foreign-owned plants. That lower pay may provide the union with an opening, Mr. King said.

But such efforts can take years to pull off, and Mr. Gettelfinger has only four more left. Among his most important actions will be to groom the U.A.W.'s next president, give a clear picture of how to handle next year's negotiations at the Detroit companies and resolve the situation at Delphi, which Mr. Gettelfinger said was "critical" to the U.A.W.

But he offers few concrete clues about his intentions. Publicly, Mr. Gettelfinger tends to be short on specifics and long on broad, macroeconomic themes like national health care and industrial policy. In that regard, he has as much in common with one of his predecessors from the 1970's, Leonard Woodcock, as he does with Mr. Reuther.

Speaking to delegates here last week, Mr. Woodcock's widow, Sharon, reminded them of one of her late husband's favorite mottoes: "What was not said was as important as what was said."