PANAMA CITY, AUG. 17 -- The opposition to military strongman Gen. Manuel Antonio Noriega suffered a setback today when its call for a nationwide business strike was widely ignored.

Only a minority of retail shops in the capital stayed closed in the morning, and some of those opened in the afternoon. The strike was somewhat more effective among industries, as delivery trucks stayed in their garages and many workers stayed home.

The strike's failure comes after 10 weeks of protests that have caused a deep slump in Panama's economy. The downturn has hurt mainly middle-class Panamanians who want Noriega to step down and, ironically, has slowed the momentum of their movement.

"The people do not have the economic conditions to continue upholding strikes of this type," said Flor Ortega, spokeswoman for the National Private Enterprise Council, the largest business confederation, which supported the strike.

The general strike was the third called by the National Civic Crusade, a coalition of more than 100 business and professional groups, since anti-Noriega protests began in early June. A two-day strike July 27 and 28 was considered 90 percent successful.

Today's action was originally planned to last three days. But as the opposition's daily car caravans and pot-banging ebbed last week, the organizers scaled it back to 24 hours.

Police Chief Col. Leonidas Macias stationed hundreds of troops along shopping avenues in a special operation he said was to "guarantee the stores stay working normally." No violence was reported.

The Defense Forces pressed some big businesses that closed in July to stay open this time, businessmen said. The Gago supermarket chain, denied permits in recent days to unload imported perishables at Panama City docks, lost thousands of dollars when onions and tomatoes rotted.

The economic crunch began to take hold in late July, economists and bankers said, as Panamanian-owned banks, about a dozen in all, stopped authorizing new loans.

Local bank credit dried up because worried Panamanian depositors moved an estimated $700 million to the United States or to foreign banks operating here, creating a liquidity shortage for several of the smaller banks.

"During July the protests were really a sporting event," said one prominent corporate lawyer. "Then suddenly the situation turned dire."

Tourism income dropped 25 percent in just two months, according to economist Guillermo Chapman, and the slowdown left at least 15,000 people jobless.

Ignacio Mallol, a prominent architect and opposition activist, said his firm's employes come in just to tap pencils on their desks, since no new projects are coming in.

"Panama is feeling acute economic anxiety," said opposition leader Ricardo Arias Calderon, head of the Christian Democratic Party.

A U.S. aid freeze that went into effect in July shook the confidence of foreign investors and customers of about 125 foreign banks with offshore branches in Panama.

Although on paper the United States had earmarked only $20 million for Panama for 1987, in fact the freeze affects $50 million that was in the pipeline, U.S. officials said.

Government and opposition forces are fighting economic battles by composing and leaking sensational anonymous documents and attributing them to the other side. One apocryphal memo the opposition circulated widely last week warned bankers that the government was about to issue a new currency. Panama now uses U.S. dollars as its paper money.

Fears that the government would freeze dollar holdings quickly spiraled, forcing Noriega in a speech Wednesday to deny any plans to issue new currency. But many depositors interpreted Noriega's mention of the possibility as a sign that it still could happen, and some panic withdrawals at local banks ensued Thursday, bankers said.

The financially strapped government, with a $3.8 billion foreign debt, has taken few concrete steps to ease the economic decline, resorting primarily to rhetoric. For example, although the business class is broadly united in opposition to Noriega, the general tried to convince business people in his speech Aug. 12 that the Defense Forces would change their style to become "the sentinel of private and foreign investment."

Romulo Escobar Bethancourt, president of the Democratic Revolutionary Party, the Defense Forces' political wing, blamed the downturn on a conspiracy by jealous Miami banks to destroy Panama's international banking center.

So far, the government's steps have been limited to lowering the price of chicken, canceling school registration fees and paying Christmas bonuses in August.

However, Escobar suggested that if the conflict continues, the government may move toward measures to shore up its union and grass-roots support. He said he will press to bring down the price of fuel by controlling the prices charged by private gas distributors and by renegotiating the contract of Panama's one refinery, which is partly American-owned.