In the early 1970s, western governments began strongly encouraging banks and business firms to supply credit, commodities and technology to Eastern Europe on a scale unknown since the end of World War II.

The assumption was that economic detente would provide the West with a measure of political influence inside the borders of the Soviet empire.

That assumption has now been strongly challenged by the Polish military's Dec. 13 crackdown on the Solidarity trade union. In the aftermath two sets of western interests have emerged.

The Reagan administration wants to use whatever leverage it has to force a removal of martial law and a return to the political revolution that was under way.

But western banks and government lending institutions want to avoid a financial crisis that would spread beyond Poland.

To hard-line anti-communists in the West, American policy options seem simple.

If the Polish military does not give in to western political demands, it should be made to get the money from the Russians to pay its debts to the western nations, or be forced into a default. In this view, the leverage is with the West, which hard-liners believe has the power to make the Soviet Union pay dearly for the crisis or face a cutoff of credit and commodities to itself and its allies.

On Saturday, a Polish official in Warsaw acknowledged the severe financial problems facing his country when he said it would need $1.5 billion in western credits every three months in 1982 to restore the economy.

But western bankers and more moderate U.S. government officials citing a total Polish debt of $26.5 billion, warn that a policy that flirts with the possibility of a Polish bankruptcy risks of worldwide repercussions.

While western politicians tend to view Polish economic problems in the context of East-West political relations, bankers tend to see Poland as just another part of a sensitive, interconnected international financial system in which debt rescheduling programs and refinancing plans are preferable to defaults in dealing with countries in need of financial rescue.

Some bankers say there are already disturbing signs that the impact of the Polish crisis is being felt beyond Poland.

In an unusual move last month, western banks refused a Romanian request to refinance some short term loans. A source in New York City said the bankers were concerned that stockholders would sue them for negligence if they increased their banks' exposure to a member of the communist economic bloc.

Romanian officials then dipped into credits from the International Monetary Fund to pay their western lenders. But, according to two sources, this had repercussions with the IMF, which decided to delay making a new credit to Romania until the situation is clarified.

Banking sources say even nonaligned communist Yugoslavia, which has good credit ratings, has run into problems covering short term obligations.

The western dilemma in responding economically to the Polish military's actions is evident in discussions taking place inside the Reagan administration's national security apparatus.

Technically, Poland is already in default on interest and principal due in 198l on the $1.8 billion owed to the U.S. government's Export-Import Bank and to private banks with guarantees from the Commodity Credit Corp.

In December, the Export-Import Bank cabled the Polish central bank, Bank Handlowy, advising it of the amount still owed for 1981.

The bank did not receive an acknowledgement until Friday, when Handlowy indicated it intended to pay.

Under a Polish-American agreement last year, the U.S. government allowed Poland to repay only 10 percent of the interest and principal it owed government agencies between April and December, with the remainder repayable under new terms beginning in 1986.

This agreement provides for the debt rescheduling to be set aside in case of "exceptional circumstances."

However, Reagan administration officials say there has been little or no support for invoking the provision, nicknamed the "Soviet tank clause," because officials fear that a formal declaration of default would absolve Poland of any responsibility to pay and would remove whatever leverage the administration now has.

Instead, top diplomatic, treasury and intelligence officials have been meeting to discuss what, if any, formal political conditions to seek when the United States and other western governments meet in Paris later this month to discuss rescheduling the Polish debt for 1982.

Complicating these deliberations is the fact that, as one official put it, the Polish debt to the West is a "house of cards."

If any of the governments or the more than 500 private banks owed money by Poland declared a default and attempted to seize Polish assets in the West, others would follow suit and the intricate system of loans would become unravelled.

Banking sources say there would be no winners since Polish funds and other liquid assets in western banks probably amount to no more than $200 million.

Western bankers have long assumed that the Soviet Union would step in to pay the debts of its East European allies rather than risk a default that could destroy the credit worthiness of all the communist nations.

But there has been no indication that Moscow has been doing anything to ease the Polish government's difficulties.

About half of Poland's total debt is owed to private banks, with West German and American banks, the largest lenders, owed $1.3 billion and $2.6 billion, respectively.

When martial law was declared last month, Poland had not paid some $350 million of the $1 billion in interest owed to all private western banks for the year. According to an analysis prepared by one New York City banker, it has since paid some $100 million, including $19 million owed to a banking syndicate headed by Bank of America.

However, other major U.S. banks such as Chase, Morgan Guaranty, Bankers Trust of New York and First National Bank of Chicago reported at the end of last week that they were still owed interest from 1981.

Several banking sources said there were unconfirmed reports that Poland was up to date on interest payments to a number of West German banks, prompting speculation that the Polish government was attempting to divide the western banking community.

Although analysts say no western bank could be bankrupted by a Polish default, a number of West German banks are heavily exposed and are expected to work hard to keep the prospects of eventual repayment alive.

This has created the conditions for a drawn-out, unprecedented war of nerves between the Polish government and western banks.

Which side has the leverage in this situation is a matter of debate among bankers. A 23-member committee of major private creditors has informed the Poles that they will not provide new loans or refinancing in 1982 until 1981 interest is paid.

However, several bankers said last week that beyond that threat they have no guarantees of getting their money back.

Meanwhile the Soviet Union has not shown what its stand will be.

"I think the Soviets are desperately afraid of the effect on their own credit," said a senior banker.

But in other respects Moscow appears to have positioned itself carefully for the crisis.

It is the least indebted to the West of any East European country. Only 7 percent of its export earnings go to cover this debt, compared with a staggering 87 percent for Poland, according to Wharton Econometric Forecasting Associates.

Meanwhile, the Soviet Union has obtained sources of food imports other than the United States in the last three years, which makes its economy somewhat less vulnerable to a unilateral American grain embargo.

In the first six months of 1981, it also withdrew an estimated $5 billion from banks abroad, thereby taking the money out of the reach of governments or creditors who might try to seize it in case of an international emergency.

Western bankers also speculate that recent heavy Soviet borrowing in short term credit markets may have been aimed at increasing the exposure of private banks and encouraging them to keep the East-West credit lines open despite a deteriorating political relationship between the two blocs.