Romania has become the second Soviet-bloc country to fall behind in its payments to western banks and companies, and its private creditors are engaged in urgent international efforts to arrange a "limited rescheduling" of at least $1 billion in hard currency debt.

Private banking sources said this week that Romania is already in arrears to western creditors by perhaps as much as $1 billion and could fall further behind if new sources of funds are not found quickly.

However, the International Monetary Fund, which suspended lending to Romania in November, is understood to have insisted on significant economic and political reforms that could lead to dramatic changes in Romania's rigid, centralized system as a condition of new help.

The Romanian financial crisis comes amid rising concern about the credit worthiness of Soviet-bloc nations in the wake of Poland's virtual bankruptcy and failure to repay western banks and governments on schedule.

U.S. bankers and officials have expressed fear that a spread of Poland's difficulties to other East European countries could undermine confidence in East-West trade and even in the stability of the international financial system. Total Soviet and East European debt to non-communist banks and governments is estimated at more than $80 billion.

Senior U.S. officials said yesterday that negotiations between the Romanian government and private bankers are being watched closely. They said a solution is in the U.S. interest because economic ties to the West are essential to Romania's foreign policy, considered the most independent in the Soviet bloc.

Nevertheless, these officials acknowledge that the Romanian credit crunch poses the likelihood of a new internal administration debate with hard-liners arguing, as they do in the case of Poland, against any new "bail-out."

In 1973, Romania became the first member of the Warsaw Pact military alliance to join the International Monetary Fund, and it has drawn on the fund on at least six occasions.

Last June 14, the IMF announced a $195 million loan to Romania to offset an unexpected drop in export earnings and said it was making available a $1.3 billion line of credit to support an economic reform detailed in documents prepared and certified by Romanian officials.

This reform was to include a cutback in foreign imports and sweeping changes in the system of subsidized prices which, in Romania's highly centralized system, are established by administrative orders and are far out of line with prices for comparable products in world markets.

In November, however, the IMF abruptly closed off the line of credit, pending resolution of several difficulties.

These included a rising bill for oil imported for Romania's petrochemical industry, a drop in agricultural production, complaints of nonpayment by western suppliers and a worsening trade deficit. In September, a banking group led by Manufacturers Hanover, Bank of America and Bankers Trust suspended plans to syndicate an $80 million loan.

Romanian officials have blamed their predicament on economic factors beyond their control, such as the situation in Poland, which they claim panicked bankers who otherwise would have continued to make loans.

That version is disputed by several private banking sources who charge that the Romanian government misled the IMF and western banks about the size of its hard currency debt and its commitment to economic reforms.

"If Romania is going to get out of this mess, then Romanian officials are going to have to get their house in order, stop the slogans and face reality," one New York banker said.

Last Sept. 23, the respected Wharton Econometric Forecasting Associates, Inc., issued a report decrying the performance of Romanian financial officials as "outrageous" and "arrogant." The report said that the Bucharest government's $6 billion estimate of its hard currency debt was "ridiculously low."

WEFA said western bankers placed the actual debt at between $10 billion and $14 billion, with at least $5 billion held by U.S. and European banks.

Several sources said Manufacturers Hanover, the only bank with a branch in Bucharest, is owed about $225 million. That bank's position reportedly has been complicated because it is the lead bank in the planned sale by General Electric of $150 million worth of turbines for a new Romanian nuclear power plant.

Another problem cited by bankers is that Romania has "front loaded" its debt, with the bulk of payments coming due in the next year or two and little hope for earning enough hard currency to cover the amounts owed.

For the last six weeks, nine western banks and IMF officials have been attempting to negotiate a plan under which they would call a meeting of international bankers in Paris or London to reschedule some loans and relieve some of the pressure.

Such a plan would include hard Romanian assurances to the IMF of real economic reform. However, this would require some liberalization of the nation's political system, which experts say is even more centralized and bureaucratic than that of the Soviet Union.