The president of Peru, acknowledging that his Andean nation is in the throes of a severe economic crisis, said here yesterday that Peru "has resumed relations with the International Monetary Fund" and received assurances of U.S. assistance in stabilizing the economy.

Gen. Francisco Morales Bermudez, here for the signing of the Panama Canal treaties, met yesterday with Treasury Secretary W. Michael Blumenthal to pursue financial discussions begun on Tuesday during an hour-long meeting with President Carter.

U.S. private banks with loans to Peru totalling about $1 billion recently expressed fears that the military government migh default - creating a precedent for other Third World countries.

In a press conference at the Peruvian embassy, Morales Bermudez said, "Our relations with the banks have always been excellent . . . and should continue to be," with any default out of the question.

The general made clear that the resumption of relations with the IMF and subsequent negotiation of a $100 million "stand-by" loan are a keystone of his austerity program. Previous negotiations broke down when Peru rejected as too onerous the measures suggested by a team of IMF experts.

Price increases and wage restrictions that Morales Bermudez had imposed in June to meet the fund's terms triggered violent riots and some measures were rolled back. Despite two breakoffs in the negotiations, a new IMF team is understood to have been left yesterday for Lima.

Morales Bermudez, 57, reiterated the armed forces' recent pledge to return Peru to "true democracy" with elections in 1980. But he added:

"We must have economis tranquility. We must have international economic cooperation for this political crossroads."

He said he could not understand how the IMF could ask Peru to impose restrictive measures found too costly in popular support even for such developed nations as Italy and Britain.

He said President Carter assured him that "U.S. economic cooperation will continue," and he cited credit programs for purchases of U.S. food exports.

A State Department official said Peru has just been granted $57 million in Commercial Credit Corp. funds which, however, are granted at virtually the same high-interest, short-term rates as commercial bank loans. He said an agreement is being worked out to permit borrowing under the concessional terms of the P.L. 480 food program.

The general, who served four years as finance minister before taking power in 1975, blamed the current crisis mainly on the weak prices of Peru's exports. Budgets were drawn up with an anticipated $2.8 billion in foreign earnings this year, but now the earnings are expected to fall to $1.8 billion, he said. He also faulted the international defenders for failing to lend to Peru at their favorable terms, until recently. Mostly, though he blamed Peru.

"I must confess that in our desire for rapid economic growth, we have spent mre than we can afford."

In addition to seeing Carter on Wednesday, Morales Bermudez played host at his embassy to the presidents of Venezuela. Ecuador, Bolivia and Columbia - the other members of the Andean Pact for economic intergration. They reaffirmed their dedication to the goal of regulating foreign investment, dispersing their own major industry and establishing free trade.