One of the few weapons at the disposal of western governments and banks to affect events in Poland is the $26 billion in debts the Polish government owes to the West.

As leverage on the Polish authorities and the Soviets, Poland's debt is a classic two-edged sword. Though it conceivably might be used to force the military junta in Poland to restore some of the liberal reforms instituted the last 16 months, this sword also could destroy Poland's credit-worthiness and gravely shake the western banking system.

And, according to western experts, these negative consequences may be unavoidable even if western governments and banks decide not to try to use the leverage this mountain of debt appears to offer.

In any foreseeable scenario for Poland, continued western credit will be crucial to economic survival, according to American diplomats and bankers and outside experts.

If the Poles default on their huge obligations they will be unable to raise any more money in the financial markets of the West, a development that would ensure Polish penury and probably prolonged economic depression, according to these sources.

This is true, the sources say, because any plan for Polish economic recovery will depend heavily on the ability to import food, raw materials and spare parts, goods that can be paid for only with hard currency. But in its current state of economic disarray, Poland cannot earn significant amounts of foreign exchange from normal trade.

Therefore, economic recovery will require access to western capital. And without economic recovery, stability in Poland will remain a distant prospect, according to these sources.

Those facts would appear to give the West considerable leverage in the Polish situation. But there is no easy way to use it. In a showdown, Poland would hold a strong hand because it could cause disruption by defaulting.

"The debtor always has the leverage in the last analysis," one New York investment banker said yesterday.

Another New York banker noted the Soviet Union also has special leverage in the Polish situation, and it works in the opposite direction of any western leverage.

The Soviets, this man noted, must provide food, oil and cash to Poland if the Poles are to have any chance of economic recovery. If any realistic plan for Polish revival would depend on western credits, it would also require a high degree of cooperation from Poland's Comecon partners, the Warsaw Pact nations.

Poland has been receiving that cooperation; the Soviets have given it more than $3 billion in cash and commodities since the Gdansk uprising in August, 1980.

"Poland is doing as much as it can" to find the money to keep current on payments to western creditors, this banker said. "You can't squeeze any more blood out of that stone." The Poles can make their debt-service payments only with substantial Comecon support, he added.

The upshot of these conflicting pressures may be a situation in which the West holds a key to future events in Poland, but can't find the lock.

Sources agreed it would require extraordinarily sophisticated diplomacy first to unify western governments and banks on one approach to the Polish problem, and then to exploit that unity without provoking a Polish default or throwing Poland into deeper chaos.

An officer of one of the biggest New York banks suggested that instead of leverage over events in Poland, the West may be lucky enough to enjoy "moments of influence" as the situation unfolds.

But those moments would not be easy to exploit, he added, questioning whether American and European banks could ever get together on a united policy.

The complexity of the situation seems to encourage pessimism among the experts.

"I don't see any realistic positive outcomes at the present time," said Prof. Richard Portes of Birkbeck College at London University, a leading academic specialist on East European indebtedness.

Portes said that in theory, Poland could bring back economic growth. The country still has its industrial capacity, skilled work force and basic economic infrastructure, he said. "It's not that difficult to turn an economy around if you can get some hold of it," he said.

But nothing can be done without the cooperation of the population, he added, and that is now an uncertain ingredient.

Even with improved economic performance, Poland faces staggering financial problems.

According to estimates in private banking circles, the Poles will need more than $9 billion during 1982 to meet interest and principal payments due on loans already outstanding, and to make minimal foreign purchases of food and industrial commodities.

If the Poles succeed in rescheduling the outstanding debts they would need to find only $3.8 billion in new credits next year. But even that "is a lot of money" when you don't have any credit rating, as an American official put it. Under present circumstances it is difficult to see where that kind of money might come from.

For the Soviet Union, the Polish financial situation appears a secondary concern, since the political turmoil in Poland so directly threatens Soviet interests. But the outcome of the financial crisis could have grave implications for Moscow, too.

Any breakdown in the system whereby western banks and governments have financed Soviet and East European purchases of western goods could create an economic catastrophe in the Soviet bloc. Already Romania is in serious economic trouble, and both Hungary and East Germany have large outstanding debts. So do the Soviets themselves.

According to bankers in New York, if the Polish debts go bad, the natural bankers' reaction will be to cut back lending to all East European countries.

But starving those countries for credit could provoke a downward economic spiral that would jeopardize repayment of the loans already outstanding. (An East European downturn would also jeopardize Soviet economic performance.) Bankers are deeply worried about the western banking system's ability to cope with defaults of tens of billions of dollars.

At present, the banking community is divided. American banks, which have loaned a relatively modest $1.3 billion to Poland, are taking a harder line than European banks which have loaned nearly $15 billion. (The Poles also owe about $10 billion to western governments, including $1.9 billion owed to or guaranteed by the U.S. government.)

If the military junta fails to reestablish order and some modicum of economic performance, the Soviets will again face the prospect of direct intervention in Poland. But with intervention would come responsibility for all Poland's debts.

This is a huge potential burden for the Soviets, even more serious in a post-intervention world of sharply increased East-West tensions.

An analyst in one New York merchant banking house said yesterday the best prospect for a happy ending to the Polish crisis would involve tacit or explicit Soviet-American cooperation based on their mutual need to restore Poland's economic health.

But he said he couldn't predict such cooperation would be forthcoming.