The continued presence of U.S. military facilities will have a bearing on future foreign investment in the Philippines, the U.S. ambassador to Manila believes.

In a recent speech to the Financial Executives' Institute of the Philippines, Nicholas Platt said U.S. and Asian investors have told him that continuing current security arrangements with the Philippines will be an important factor in the nation's investment climate.Talks are being held on the future of Clark Air Base and Subic Bay naval station, both of which are the largest such military bases outside the United States. The current agreement expires in 1991.

Mr. Platt said the American Chambers of Commerce in the Asia-Pacific region passed a resolution recently emphasizing the importance of negotiating the continued life of those bases.

He said he is generally optimistic on the Philippines' investment outlook, calling this ground floor time for investors.

As security analysts like to say, the down-side risk is limited, and the upside potential great, he said.

The Philippines recorded an $882 million trade surplus with the United States last year, up 12 percent from the $787 million surplus of 1986.

Shipments under the Generalized System of Preferences, or GSP, were a big factor in the increase. The GSP program allows many exports from developing countries into the United States without payment of duty.

Such exports by the Philippines totaled $329 million last year, up 43 percent from 1986. Of the 142 countries qualified under GSP, the Philippines is now the 10th-largest beneficiary.

Mr. Platt noted that all 11 Philippine requests for extensions of zero-duty GSP benefits were granted last January. They include cigarette lighters, bananas, sugar and wooden veneer panels.

Outside GSP, Philippine textile exports to the United States last year came to $620 million, up 38 percent from 1986. Much of this arises from a substantial increase in garment quotas agreed in March last year.

There is much room left at the upper end of the textile quota, which is attracting manufacturers from countries whose quotas are full, Mr. Platt said.

Businessmen from Taiwan, Hong Kong, the European Community and Japan are starting to invest more, he said, declaring: This country is uniquely positioned to leap into the void left by the graduation of the Dragon economies from GSP.

Asia's Four Dragons - Hong Kong, Singapore, South Korea and Taiwan - will lose their GSP benefits in January.

Mr. Platt said the government of Corazon Aquino came to power with a strong free-market and private-sector orientation. Since 1986 it has launched reforms that touch nearly every corner of the economy.

The government has liberalized trade in several commodities, including fertilizer, wheat and feed, and abolished most export taxes. It also has implemented more than 18 tax reform measures to improve efficiency.

The ambassador acknowledged that the Philippines probably loses some investment because it generally permits no more than 40 percent equity in a company, less than allowed in Malaysia, Thailand or Indonesia.