Poland announced today that there will be unspecified cutbacks totaling $400 million in public spending on industry and administration as part of an austerity move to help finance the recent labor settlements and to reorder the country's budget.

Meanwhile, a spokesman for Poland's Catholic Church said broadcasting of Sunday mass over the state radio will begin next Sunday. Resumption of the broadcasts, halted 36 years ago when the Communists took control of heavily Catholic Poland, was one of the strikers' demands and was approved by the government.

The $400 million budget cutback announced today appeared small in relation to what the Warsaw government eventually will have to pay for the higher social benefits it promised workers to end the wave of strikes this summer, and it may be just a foreshadowing of further spending reductions in coming years.

The government's pledge to raise wages and benefits for all workers has been estimated by officials to cost $3.7 billion. Moreover, losses to production as a result of the strikes reportedly cost the economy $1 billion dollars in August alone, plus well over $500 million in unrealized trade.

Polish authorities fear many of these losses will be difficult to recover, especially since labor unrest continues in parts of the country, frustrating the recovery effort.

Already heavily in debt to the West, Warsaw has turned to its communist neighbors for financial assistance and emergency supplies to alleviate worsening shortages. It was announced earlier this week that the Soviet Union has loaned Poland the equivalent of $690 million in a mix of extra supplies, hard-currency credits and deferment of payments owed to Moscow by Warsaw.

East Germany has also rushed additional goods to the Polish market. Today's Polish press reported high-level missions by Warsaw officials to Bulgaria, Czechoslovakia and Yugoslavia, apparently to explain the developments here and to arrange for additional assistance.

Announcement of Warsaw's spending cutbacks appeared in a report by the official Polish press agency PAP on Monday's meeting of the Council of Ministers. At the meeting, "it was stated that the present difficult economic situation of the country and the necessity to implement social programs required great savings in al spheres of both economy and administration," PAP said.

The agency gave no details about where the cutbacks would be applied. It said simply that the government's 1980 program would be trimmed by $400 million, which, together with other unspecified "tasks" that PAP said would be implemented "will lead to a savings of $1 billion to $1.1 billion."

"The program has been adopted only temporarily," PAP said. "It is expected that within its framework, enterprises and firms will take steps to limit unnecessary expenditures as well as to ensure more effective management."

In other developments, the Catholic spokesman said Polish radio would begin regular weekly broadcasts of Sunday mass in fulfilment of a government pledge to give Poland's Catholic Church access to the mass media.

With three-quarters of Poland's population said to be Catholic, the church retains considerable influence in this communist state.

The government has not told the Polish public when the broadcasts would start. A brief PAP report today said only that the government, in cooperation with the church, is making "technical and organizational preparations" for radio coverage of the Sunday mass.

Meanwhile, at the Warsaw District Court, where workers yesterday were instructed by the government to register their new independent trade unions, a spokesman today reported many inquiries.

[Two moves toward formation of autonomous unions were reported by PAP, according to Western news services. Workers from the Katowice steelworkers presented an application for recognition as an independent union, PAP said, and representatives of the 148,000 member Union of Longshoremen and Seamen passed a resolutin to withdraw their organization from the Communist-controlled Trade Union Council and establish it as an independent union.]

Free unions were among the major concessions won by strikers last month, but while thousands of workers have signaled their intention to withdraw from existing official trade groups, the new unions remain in an embryonic and somewhat confused state.

Organizers in Poland's larger industrial cities are trying to draw various disenchanted worker groups together into new regional union structures. In Warsaw, for instance, two such central organizations have sprung up, one called Mazowsze, which represents a broad range of factory and institutional groups, and another representing teachers, technicians and scientists.

The theory behind these new organizations is strength in numbers. But some of the newly formed independent branch unions are said to have reservations about joining a central council that, potentially, could become as bureaucratic as the official council of trade unions against which the workers struck.

Some union organizers objected in interviews to having to come to Warsawa to register -- a requirement apparently intended by the government to get a precise reading of the size of the new movement.

Moreover, while the court has been given the right to reject a new union if its existence is seen as violating the Polish constitutions, some workers complained that no deadline was given for the court to render its decision.

Polish authorities insist they have no intention of inhibiting development of the new unions. Polish television tonight showed an interview with the vice chairman of the Warsaw court, who said he had assigned to the new registration section "the most eminent lawyers with much experience" to advise the fledgling union groups on correct legal procedures.

Representatives from new union groups all over Poland plan to meet tomorrow in Gdansk, the Baltic seaport whose shipyards were a center of militant labor activity in August, to discuss common problems and consider a model charter now in draft form for the new unions. Also on the agenda is the possible formation of a national umbrella committee to coordinate the independent movement.

Organizers say they are anxious to compare experiences so far with their counterparts elsewhere in Poland.