A new wave in American investment in the Philippines would have been expected this year following wide-ranging economic reforms aimed at promoting new industries. But a highly publicized bombing incident occurring during a conference of American travel agents, may have stemmed the tide.

The bombing was one of the most recent in a series of terrorist incidents which has many wondering whether this will be the next Iran or the next Korea.

But American businessmen here, though wary of political jolts, feel confident the nation's technocrats will keep the economy on even keel and uphold the favorable environment for the multinationals.

None of the Americans we interviewed here and in the U.S. considered an overthrow of Ferdinand E. Marcos imminent. Marco became president in 1965 and declared martial law in 1972.

The opposition, they say, is fragmented, offers rhetoric instead of specific proposals, is supported mainly by the middle class of Manila and has failed to win over the masses in the countryside.

A second, more violent and better organized source of opposition comes from Moslems in the south who are seeking separation. A recent report that the armed forces have brought the insurgency under control raises the likelihood that Marcos will lift martial law in 1981 as he promised, which would in turn defuse the opposition in Manila.

The Americans do not discount the possibility, however, that Marcos sooner or later will no longer be in the picture. Apart from the First Lady, Imelda Romualdez Marcos, who holds a number of government posts including Governor of Metropolitan Manila, presidential envoy plenipotentiary, Minister of Human Settlements and member of ("Bongbong"), who is a provincial vice governor, Marcos has not groomed a successor.

But even with the heating up in opposition and the recent bombing, "The situation is normal; there has been no disruption in our activity," said George Suter, president of the American Chamber of Commerce in the Philippines. "The dissidents haven't focused any attention on foreign business."

If there is an adverse effect, it is that companies will be scrutinizing more closely projects requiring new investment, said Suter, who also is general manager of Pfizer, a pharmaceutical company.

Pfizer, which has been in the Philippines since 1954 and recently opened a new plant, plans to invest an additional $750,000. "I'm glad we got our investment approved three years ago," Suter said. "I could envision some problems if we sought the allocation now."

Even if the "worst case" scenario should occur and Marcos were replaced, he said, "there would be a smooth transition. Here (as in Korea), they are committed to capitalism. We give high marks to the technocrats. They are very pragmatic. Many have been trained in the U.S.," Suter said.

Suter estimated American business has $2 billion invested in plants and facilities in the Philippines, principally in electronics, pharmaceuticals, food processing, textiles, automotive manufacture and oil refining. The Chamber has 205 American corporate members but the population of the American business community, spread throughout the country, numbers less than 5,000 with dependents. U.S.-Phillipines trade amounted ot $2.1 billion in 1978, or 26.2 percent of Philippines' total.

There were two periods of U.S. prominence in the economy -- the 1950s and 60s, when the country cultivated food processing, pharmaceuticals, tire production and oil refining. Then in the 1970s, the government shifted emphasis to export processing, electronics and garments.

In 1973, a presidential decree set out incentives to entice multinationals to establish regional or area headquarters in the country. About 250 companies, including Singer, took advantage.

At the beginning of this year, the government launched a dramatically different economic program, modeled after Taiwan and South Korea, aimed at generating new industries and nontraditional exports. The main elements of the program: extending duty-free privileges, reducing bureaucratic barriers, and encouraging the formation of large trading companies.

Despite an extensive campaign to draw U.S. business, "there hasn't been a giant wave, only continuing interest," commented George Paine, Philippines country specialist in the International Trade Administration.

Suter does not see a new wave for American investment, either. On the other hand, "The in-place investors have run out of capacity and are reinvesting." Scott Paper, for example, is investing $7 million. "International business is not in transition," Suter said. "The change is more internal."

Many of the American companies which in the past produced for the local market or for export to the U.S. are now looking to expand into exports to the region.

Texas Instruments, which this year began manufacturing semi-conductors and transistors on a 40-acre site in a newly built duty-free export processing zone, plans to start manufacturing consumer products such as calculators for export to world markets. "We are proceeding as scheduled along long-range plans for our plant in the Philippines. There have been no long-term interruptions in operations and I expect none," said Dr. Rolf Haberecht, manager of overseas plants.

General Motors, which manufactures automatic transmissions and assembles cars and light-duty trucks, is pressing ahead with a joint venture with Isuzu of Japan to increase production and ultimately develop more exports.

The venture, a spokesman commented, "has been successful." So far, the plant exports little to other areas and is primarily for domestic consumption. "The Philippines has been a good market. We are still enthusiastic. "We feel enough people there are concerned about the country to make it work. There are good, intelligent people who don't want to see it come apart. We have faith in the leadership." He added that even if Marcos were ousted, "there would be a smooth transition."

Ford manufactures cars and trucks for domestic consumption and has experienced "a severely depressed market. "It isn't as large a market for cars and trucks as in the past and as one would expect it to be," a spokesman said, adding that this has occured over a long period of time. Ford has a stamping plant and an assembly plant where a Fiera "jeepeney" -- is produced and "is not backing away". The company is planning to expand sales of the Fiers to Indonesia and other Southeast Asian countries. But 1979's production of 9,700 cars and trucks was down substantially from 1978's level of 13,000 vehicles. "The manufacture of parts and vehicles is controlled by the market-place and government regulations, more than it is by the peacefullness of society," he said.

Indeed, Pfizer's own sales were "10 percent behind plan, but still up 13 to 14 percent over the last year" -- another measure of the strength of consumer demand -- Suter said that of the 13 percent, 9 percent reflected inflation and 4 percent was a volume increase.

The softness in the consumer market suggests that opposition to Marco's regime may go beyond the issue of martial law and a politcal power play and could indicate more fundamental ills. The weakness is due in part to population growth, softness in world prices for coconut and sugar and world recession. But it also is due to rising consumer prices. Many charge that the middle class -- the core of the oppositon -- is being squeezed out by the power elite surrounding Marcos who control prices. "There is rich and poor, nothing in the middle," said an Australian businessman who was leaving the Philippines after 10 years because of the rising cost of living. "A clique owns the stores, raises prices weekly and the people have no choice but to pay. Bread lines are forming and robberies are up tremendously".

A Filipino also reflected on the demise of the middle class. In this country, middle class is defined by such items as televisions, air conditioners and stereos. Installment buying helps, but latley people cannot even afford to buy a television with four years to pay."They buy the antenna first, because they may eventually get a television cheap."

He said with agrarian reform, people in the countryside are contented. Even in the cities, the basics of food, clothing, shelter, education and health have been provided. "But people are hungry for power. They are thinking they can go back to the old system. It is human nature." But many remember back to before martial law, when political corruption was pervasive, everyone carried guns and a traffic accident was settled by a bullet, and people lived in impoverished conditions. "Democracy was a flop. It didn't work in a Chinese-oriented society, and despite our 300 years under Spanish rule, we stll have Chinese blood. "The opposition makes objections. But no one has come out with a plan. Between two evils, we choose the lesser one."

Paine in the International Trade Administration, does not believe the opposition will succeed in ousting Marcos. "The Philippnes is totally different [from Korea and Iran]. The government has its problems but [the terrorism] is not a threat to the government itself. It is an isolated situattion. Unless there is a real catastrophe, foreign business community would likely go on. The technocrats would continue to run the country. There would be a change in the faces of the Filipinos -- the Marcos family may be out, and someone else's in. There are people who prefer to be in power themselves. It's a toss-up whether Marcos will stay. But it is important to politics and not too much to economy and business," Paine said.

Marcos has suggested he may lift martial law in March 1981 if security and economic stability can be assured.