A high-level U.S. aid delegation arrived today to join a stream of other foreign missions intent on helping the new Philippine government deal with the debt-stricken economy bequeathed by ousted president Ferdinand Marcos.

Even before the mission headed by M. Peter McPherson, administrator of the U.S. Agency for International Development, landed here, talks had begun between Philippine officials and the International Monetary Fund.

Decisions by the International Monetary Fund often influence actions by other international financial institutions, donor governments and commercial banks.

These governments and institutions have indicated their willingness to help President Corazon Aquino's government combat an economic crisis of such proportions that, according to one economist, the economy would have to grow at an annual rate of 4 percent until 1992 before the Philippines would regain the 1982 standard of living.

Last year, the economy is estimated to have shrunk by about 4 percent.

Equally significant for financial specialists was the presence here of David Pflug, a Manufacturers Hanover Trust Co. senior vice president and chairman of the advisory committee of more than 300 commercial banks owed most of the country's $26 billion foreign debt.

So far, only Australian Foreign Minister Bill Hayden has announced more aid, doubling assistance to $17.5 million this year.

But soon after Marcos fled the country Feb. 26, Japan, a major aid donor, dispatched Deputy Foreign Minister Shinichi Yanai to Manila to confer with Aquino and other officials before flying to Washington last week for consultations with U.S. officials on economic cooperation.

The actions of the United States and Japan, the two largest aid donors to this nation of 55 million people, could demonstrate their confidence in the Aquino government and, according to western diplomats, are likely to influence the IMF, the World Bank and commercial banks.

Economists and western diplomats agree that the economy, which has stagnated since the 1970s because of a world recession and serious mismanagement by close associates of Marcos who benefited from his friendship, is one of the key issues facing the new government.

"The Aquino government has to show that things are getting a little better -- first and foremost with the economy -- in a matter of months," one western diplomat said.

The U.S. mission, which includes high-ranking Treasury, State Department and Pentagon officials, will not "make any specific decisions" during a week-long visit but will "help furnish recommendations to President Reagan as to how the U.S. can best support Philippine economic efforts and plans," an embassy communique said.

Diplomatic sources said it was "too early" to mention specific amounts of western help, although Rep. Stephen J. Solarz (D-N.Y.) predicted that Congress would provide more than the current $180 million annual aid.

The sudden collapse of the Marcos government left Aquino and her key financial advisers no time to prepare transitional position papers.

But western diplomats and financial specialists said they were encouraged by the continued tenure of Central Bank governor Jose Fernandez. Similarly welcomed was Finance Minister Jaime Ongpin, a businessman well acquainted with international finance and a representative of the modern business sector, which played a major role in helping Aquino to power.

Central Bank sources said the IMF team that has arrived, and a second team scheduled to arrive next week, would be conducting a major political and financial review. The second team is expected to decide whether to release the final installments, worth $230 million, of a standby loan that expires in June. Such a mission had been planned for February but was postponed because of the country's political turmoil.

Fernandez and Ongpin have indicated that they will argue for easier repayment terms.

The IMF negotiators already here reportedly were exploring the possibilities of a new standby agreement or a new program. The current program, agreed upon in December 1984, is due to expire June 13.

Central Bank sources suggested that any new funding would likely be slightly less than the current $650 million IMF loan program, agreed to by the Marcos government and the fund in December 1984, in keeping with the Aquino government's desire to reduce foreign borrowing.

Western diplomatic sources suggested that the fund might be willing to allow the new government greater budget leeway to absorb the $250 million to $300 million in public funds that Marcos reportedly spent on his reelection campaign.

Ongpin also has indicated that he would like to reschedule debts with the World Bank and commercial banks when he travels to Washington in April for the regular meeting of the interim committee of the fund and the development committee of the World Bank.

Commercial banks are owed between $15 billion and $16 billion of the outstanding rescheduled Philippine debt and have received no payment on principal since October 1983. Interest payments alone account for an estimated 50 percent of export earnings.

Although Central Bank sources reported that more than $50 million had entered the country since Marcos left, one of several indications of improved business confidence in the new government, the sources said this development was not expected to do more than stop the economy's two years of negative growth.

At least $700 million was sent abroad illegally since 1983, according to Central Bank sources, who said undervaluing exports and overvaluing imports caused a much larger capital drain.