After the collapse last of the Belgian government, it was noted that, for once, a government here had fallen over the sort of hard economic problems besetting most countries in the world, rather than the traditional rivalries between Dutch- and French-speakers that have toppled 29 Belgian governments since World War II.

Belgium this time was an early European casualty of the West's economic slump. While much of the world is economically troubled, the situation in Belgium is among the most worrisome as a result of political inaction against a mounting front of problems. They include a severe balance of payments deficit, widespread industrial fatigue and welfare payments that have outstripped the country's ability to pay.

The country's conservatives are at odds with the powerful trade unions over tough mesures to deal with what many regard as a near-disastrous national condition. The international community rendered a no-confidence judgment recently by speculating heavily on a currency devaluation.

In an unprecedented move, Belgium's King Baudouin last week summoned the leading political, business and labor figures of his crisis-ridden country for a royal pep talk. It was a risky initiative by a basically powerless monarch, who upset some politicians and pundits for appearing to step outside the normal channels of Cabinet government to get his message across.

But the brief address succeeded in dramatizing the gravity of the moment. With only a bit of overstatement, the king declared that Belgium had been presented with a "war for the survival of our economy."

Managing affairs in this small central European country has never been easy, due primarily to Belgium's rival language groups. Dutch-speaking Flemings dominate the northern half of the country and French-speaking Wallons dominate the southern half.

But the current crisis differs from past splits. "This is the first crisis we've had not based on a fight between the two people," said Guido Fonteyn, political correspondent for the Flemish daily, De Standaard.

"This one has been caused by contrasting left-right political views on the economy."

An American analyst said, "This is a fundamental crisis on fundamental economic issues. It has brought Belgium's long-simmering economic problems to a boil."

The basic problems are these:

Unemployment keyed to Belgium's aging, recession-hit heavy industries is expected to swell by 100,000 this year to reach 477,000 -- about 10.5 percent of the work force -- giving Belgium the highest jobless rate in the European Community.

The cost of maintaining the country's generous unemployment benefits and social service had already overwhelmed the budget. The federal deficit on current expenditures is predicted to more than double this year from $2.6 billion $5.8 billion. Since 1978, Belgium has been borrowing from abroad to make budgetary ends meet.

As a result of the borrowing and the loss of international industrial competitiveness, Belgium's current account on its balance of payments is forecast to slide further to $6.8 billion this year, which at roughly 6 percent of the gross national product exceeds any other Western European country.

Judging from the activity had the veneer of wealth in this capital city, Belgium would not seem on the surface to be in deep trouble. There in a striking lack of any sense of crisis among many Belgians, reflecting perhaps the focus on personal interests in what is traditionally a conservative and bourgeois country.

Belgian wage earners generally have been cushioned against a weakened economy by a national system of wage indexation that has passed on increases in the cost-of-living index. Sizable unemployment allowances help the jobless.

Much of the cost of Belgium's plight has been borne by industry. which has had to pay among the world's highest wages (25 percent above those in the United States on average) and steep interest rates (the price of keeping a strong franc). Investment capital is shying away from new commitments in Belgium, and foreign firms are pulling out.

While the signs of economic erosion have been evident for some time, the country's intractable political problems kept the government from focusing on the economy.

Agreement last August on constitutional changes and a regionalization plan to grant limited autonomy to Flanders and Wallonia finally freed government leaders to spend more time considering economic matters. But the issues are linked.

Wallonia's sputtering coal and steel industries in southern Belgium constitute the central trouble spot. Once the cradle of Belgium's 19th-century industrial preeminence, these industries today are seen as weighing down the rest of the country, while Flanders has become economically important due to investment by petrochemical and other high-growth firms.

The Flemings resent expensive government subsidies to Wallonia, and the people of Wallonia resent the ascendancy of Flanders.

A start on a three-stage program of national economic recovery -- involving wage restraint, spending cuts and reindustrialization -- was made this year when labor and business agreed to limit wage increases for two years.

At a subsequent negotiating session of ministers two weeks ago, the center-left coalition government of Social Christians and Socialists agreed to spending cuts of roughly $3 billion over three years.

These were widely perceived as insufficient, however, and rumors of a Belgian devaluation began to fly.

Appearing to panic, the prime minister, Wilfried Martens, sought crisis talks early last week in which he pressed for more severe measures, the most drastic being suspension of wage indexation. The Socialists and their labor union constituents balked.

Martens, 44, who in two years had presided over four governments, submitted his resignation for the fourth time. The king picked 47-year-old Marc Eyskens, the brilliant but relatively inexperienced finance minister and, like Martens, a member of the Flemish Social Christians, to form a new government.

No one is optimistic about the prospect of Belgian economic recovery in the near term. Essential to any effective new program must be tacit agreement from Belgium's labor unions to change the indexation system and political courage from government leaders to cut social welfare spending.