Belgian Premier Leo Tindemans, plagued with strikes by unions opposed to his austerity measures and by federalist demands to split his country into French and Dutch-speaking regions, must decide this weekend whether he will rule with a minority government or call for new national elections.

Tindemans lost his majority Thursday when he expelled a French-speaking party, the Rassemblement Wallon, from his centrist coalition for refusing to back the government in a budget vote in Parliament. This left the government two votes shy of a majority in the 212-seats congress.

The Rassemblement Wallon protested the government's flagging efforts to grant more autonomy to the country's three main regions - Flanders, Wallon and Brussels.

The drive toward a federated Belgium has gained momentum recently not only because of aggravated lingulstic problems, but also through divergent economies.

The French-speaking Walloon area, depressed for years by its declining coal and steel sector, requires urgent aid to build a new industrial base and retain hard-pressed workers:

People in Flanders, the Dutch-speaking area, contend on the other hand, that they shoulder an unfair proportion of the tax burden. The prosperous Flemish comprise 55 per cent of the country's population, but pay 70 per cent of its taxes.

The Brussels region is the country's spoiled yet unvloved child - envied by poor Wallons for its rapid evolution into a wealthy metropolis, but despised by Flemish who find "the new capital of Europe" dominated by French-speaking Belgians.

The Tindemans government took office in March, 1974, after general elections brought down the Socialists, and promised swift action towards "regionalization" - a euphemish for a federated Belgium.

But troubles have erupted over the status of Brussels and how its billingual charter, which requires all official work to be transacted in Dutch and French, would apply in a federal state.

The Flemish want two distinct regions, with the country and Brussels divided into Dutch and French-speaking parts. Walloon politicans seek to split Belgium into three areas - Flemish, Walloon and Brussels, with Brussels probably drifting into the French-speaking camp.

Tindemans appointed a 36-member committee to study the issue, but it has failed to resolve the widely differing views of the linguistic factions.

The government also faces mounting labor agitation as a result of proposals to increase sales tax on cigarettes, liquor, gasoline and "luxury items."

Strikes involving 300,000 workers brought bus and streetcar service to a halt yesterday. Last week, the first national train strike in 17 years caused thousands of persons to miss or be late for work.

Tindemans announced yesterday that he will tell the Belgian Parliament on Tuesday whether he plans to continue to rule with a minority or ask Belgium's King Baudouin to dissolve Parliament.

In the latter case, new national elections would probably be held in late April, one year ahead of schedule.