BRUSSELS -- Jesse L. Jackson, as usual, put it most colorfully.

U.S. taxpayers, among them World War II veterans "who today cannot get hearing aids, glasses, teeth or a balanced diet," are spending $150 billion a year defending Western Europe, the presidential candidate told NBC's Meet the Press last month. Yet Europe, he said, refuses to pay its share of the bill for collective western defense.

Vice President Bush agrees. "We must ensure that they carry their fair share of the load," he told interviewers last summer. So does Michael S. Dukakis, who told the Christian Science Monitor two weeks ago that the allies must do more to bear their "fair share" of the burden.

The charge that European members of the North Atlantic Treaty Organization have been freeloading at American expense has been made by every candidate since the long U.S. presidential campaign began. In these times of deficits and the falling dollar, it has been a sure applause-getter from audiences of the left, right and center.

The sound of all those American hands clapping has had a disturbing effect on this side of the Atlantic. The burden-sharing issue is not a new one to Europe, but for the first time, Europeans are beginning to believe that the United States is gearing up to do something about it.

"Reagan has been quite good as far as Europe is concerned," said Martin McCusker, military analyst at the Brussels-based North Atlantic Assembly of NATO parliamentarians. Concerned with building the U.S. defense budget, the administration has sidestepped insistence from some quarters in Congress that the Europeans pay more for their security so Americans can pay less.

The Reagan administration is the latest in a long line to seek to ignore congressional suspicion, beginning the moment Europe climbed out of its postwar destitution, that advantage was being taken. Every year from 1966 to 1973, then-senator Mike Mansfield of Montana introduced a resolution insisting that a "substantial" number of U.S. troops could be withdrawn from Europe without adversely affecting western security.

Despite substantial congressional support, executive branch pressure succeeded each year in defeating the Mansfield amendment.

"That can't happen in the next administration," McCusker said. Because of the deficit alone, the new president "is going to have to address the issue seriously."

At the same time, as NATO begins the process of adjusting to negotiated reductions in nuclear weapons and increased dependence on more expensive conventional defense, he said, "any debate about strategy will become a debate about burden-sharing."

The stakes in such a debate are high, with an increasing number of U.S. analysts saying that significant cuts in the more than 300,000 U.S. troops in Europe are the logical response both to unequal spending and a diminished risk of conflict with the Soviet Union on the European central front.

As a superpower, these analysts argue, the United States must devote ever more military resources to new fights against terrorism and to conflicts beyond Europe, such as in the Persian Gulf. If the Europeans believe that troop levels in Europe must be maintained, they should supply the troops themselves, the analysts say.

That argument is universally opposed by the allies, as it was during the time of the Mansfield amendment, as a dangerous form of decoupling that will change the security equation in Europe and put the West at a disadvantage just when serious bargaining with the Soviets over conventional-force reductions seems ready to begin.

Some European officials warn that a U.S. pullback could drive them into the arms of the adversary. "I am certain that the more you reduce the U.S. presence in Europe," said Belgian Defense Minister Francois-Xavier de Donnea, "the more Europe will be forced to look for compromises with the Soviet Union, and not necessarily those that are in the interests of U.S. security."

That talk angers Americans such as Rep. Patricia Schroeder (D-Colo.), who chairs the panel of the House Armed Services Committee that deals with the issue. "We have major disagreements with {the allies} about what strategies are appropriate, what our collective interests are and how great the Soviet threat is," Schroeder wrote in a recent column in The New York Times.

"The voters are beginning to figure things out," Schroeder wrote. "We are subsidizing the security of our major trading partners while they are cleaning up in international markets. Our allies are not likely to spend more as long as Uncle Sam is willing to do it for them."

For their part, the Europeans are angered at the implication that the United States is doing them a favor by helping to defend Europe. It is in America's interest, they argue, to draw its defensive border on the eastern side of West Germany, "instead of at Chesapeake Bay," McCusker said.

"I don't object to the U.S. putting the question on the table," de Donnea said. "The U.S. should tell us frankly what it believes. But we should also tell them that some of the ideas floating around there are too simplistic."

Beyond arguments over strategy, the scale of the threat and the future of arms control, however, many Europeans dispute the arithmetic leading to the charge of freeloading.

NATO has no standard measurement for assessing either the size of its defense burden or the relative shares that each member should be carrying. Depending on how statistics are juggled, the United States is doing more than twice as much, about the same as, or somewhat less than its European allies.

According to NATO figures, the United States last year spent 6.5 percent of its gross domestic product on defense. Among NATO's larger European members, the next highest was Britain, at 4.8 percent. Down in the spending basement were Denmark and Canada, with 2 percent, and Luxembourg, with 1.2 percent.

Schroeder points out that despite NATO agreements since 1978 that each member would increase defense spending by 3 percent annually, American spending rose in real terms by 5.7 percent annually from 1978 to 1985, while average allied spending has never met the target.

But the Europeans argue that those figures are misleading because they support the "free-ride" case by including the big, unilateral U.S. buildup under Reagan, but ignore the substantial post-Vietnam U.S. defense winddown in the 1970s, when European expenditure was steady. The 3 percent target, they recall, was originally decided not as a means of prodding the Europeans, but to press for an American increase.

Another distortion is caused by fluctuating currencies. Although NATO builds in some compensation for shifting exchange rates, a NATO economist pointed out that "when the dollar is very weak, it looks as though Europe is doing much more. When the dollar is strong, it looks as though Europe is doing much less."

At the same time, even allied governments such as Britain that consistently have met higher targets and have urged their fellow Europeans to do more, resent the freeloading charge.

"In fact, we have a good story to tell," British Foreign Secretary Geoffrey Howe said in a speech last month. "European defense budgets grew by 30 percent in real terms between 1970 and 1985, more than twice as fast as the United States."

A British Defense Ministry official noted that "in terms of combat-ready troops in Europe, the Europeans provide 90 percent of the manpower, 85 percent of the tanks, 95 percent of the artillery {and} 80 percent of combat aircraft and have a mobilization strength of 7 million troops, compared to 3.5 million in the United States."

West Germany has long argued that much of the cost to Bonn of allied defense is not reflected in budget figures. The West Germans include on a long list of "intangibles" the $22 billion worth of buildings and land turned over to foreign bases, the large number of NATO exercises held on West German soil each year and the 600,000 air sorties flown in West German air space. Of these, 100,000 are flown at dangerously low levels, resulting this month alone in three crashes and the death of a pilot and a West German citizen.

"These are burdens on the citizens of our country that you can't measure in dollars or marks," said a senior West German Defense Ministry official.

Some European countries also have military conscription, which they maintain not only removes productive capacity from their economies but also gives a skewed picture of relative contribution, because pay rates are so low compared to salaries in the U.S. volunteer military. "Forty thousand serve in our military each year for practically nothing," said Belgium's de Donnea. "They get paid 125 Belgian francs, the equivalent of $4 a day."

Even such intangibles, however, cause bickering. Many U.S. officials privately describe Europe's conscript armies as less efficient than American forces. Europeans, on the other hand, contend that their conscription from the general pool of young males gives them armies with higher average intelligence and ability than what they see as bottom-of-the-barrel U.S. volunteers.

While the West Germans complain about property damage caused by maneuvers, the government submits, and the U.S. military pays, damage claims that have totaled an average of $29 million annually. The Americans have begun to question whether West German civilians, particularly farmers whose land is used for exercises, are trying to cheat them.

"We don't want to offend an ally," Sen. Alan J. Dixon (D-Ill.) said at a recent Senate subcommittee hearing, "but we want to save money if possible." Dixon said a West German general once told him that in West Germany "the oldest son inherits the farm, the next in line gets the maneuver damages."

The resentments provoked by the the burden-sharing debate have led analysts to advocate doing away with assessments based on quantity of monetary input.

In the first place, no matter how much they are berated, it is highly unlikely that the Europeans are going to spend more.

In Denmark, the minority government is deeply in debt and has lost five successive years of defense-budget battles with its left-of-center opposition. Early this year, the two frigates that comprise Denmark's ocean-going naval capacity were taken off active duty because of lack of funds to refit them. Fuel for military vehicles is so scarce that the Defense Ministry last month began assigning camouflage-painted bicycles to soldiers in selected units, instead of jeeps and trucks.

"I'm not sure even a partial pullback would create a big wave of European spending," said Belgium's de Donnea. "We too have very tough budgetary constraints -- we also have gone through a crisis. We all have to support a lot of social spending, and there is a lot of unemployment in Europe."

Secondly, the NATO economist said, "suppose we persuaded the Danes and the Belgians to do a lot more. What would that mean? In fact, very little. When you look at the size of their defense budgets, they contribute a relatively small amount. Even if you got them to do more, it wouldn't make a lot of difference.

"What the Americans really are talking about are the French, the {British}, West Germany and Italy. Only if those spent more would there be a big impact. It could be argued, though, that those four have done pretty well" in increasing expenditures and meeting targets.

Finally, the analysts argue, even a reduction of tens of thousands of U.S. troops in Europe would not constitute much of a savings for the American taxpayer. The U.S. soldiers would "still have to be based, and paid for, somewhere," said a NATO planner. "It would be a symbolic gesture with political repercussions, but not much economic repercussion."

But even while they complain about the unfairness of it all, many Europeans say they can read the handwriting on the wall.

"It's no good saying that people like {Schroeder} have got it all wrong," McCusker said. "Underlying it all is exasperation with the Europeans. They're saying Europe has got to do more, and the only way to get them to is to threaten them. I think that's true."

One of the problems of assessing relative NATO contributions, a senior alliance planner said, is that "while everything is cast in terms of the fairness of the burden, the total burden itself has never been spelled out."

Instead of determining what defense is necessary, then dividing up the responsibility for providing it among individual members, NATO works the other way around. Each member provides a list of assets that it is prepared to provide and allows NATO, within sharply drawn limits of national sovereignty, to decide how those assets should best be deployed for the common defense.

Among reform proposals to provide new ways of calculating member contributions to NATO is a system of task specialization to permit each ally to assume commitments that they can best comply with and give up other, more expensive defense roles for which they are ill-suited.

De Donnea agreed, for example, that Belgium does not necessarily need to have its own ocean-going frigates, a huge expense that may satisfy national naval pride but makes only a minor contribution to the protection of western sea lanes.

There are also calls to expand collaboration in building equipment to reduce waste and overlap. With dozens of contractors producing their own ships, planes, tanks and even bullets, the only thing that NATO countries have in common is the air in their tires, NATO Secretary General Lord Carrington once said.

These measures, and others, would help quantify effective defense output, rather than monetary input, while incorporating such individual qualifications as intangible contributions and relative national prosperity.

None of these ideas is new, and most of them have been the subject of previous or ongoing NATO studies. Sen. Sam Nunn (D-Ga.), a leading proponent of the output-measurement strategy, sought to incorporate them in his 1984 amendment tying U.S. troop levels to extra Western European effort.

The Reagan administration, in large part to head off Schroeder's subcommittee and put the problem at least temporarily to rest for what it hopes will be a Bush administration, has created a high-level task force headed by Deputy Defense Secretary William H. Taft IV.

Earlier this month, letters went out under Reagan's signature to all NATO government heads and to Carrington noting that Taft will be visiting all of them in coming months to talk about rising concern about "equitable burden-sharing" and ways for NATO to make more effective use of existing resources.

The growing consensus in Europe is that it may be an idea whose time has finally come.