Foreign Minister Miguel D'Escoto said today that Nicaraguan officials had spoken by telephone with relatives of two Americans killed Saturday when the helicopter they were flying in was shot down over Nicaraguan territory.

D'Escoto said at a news conference that he had spoken with Rose Powell of Memphis, Tenn., mother of James Powell III, also of Memphis, and other Foreign Ministry officials had spoken to Dana Parker of Tennessee, the father of Dana H. Parker of Huntsville, Ala.

D'Escoto said that both Powell and Parker had expressed a desire that their sons' bodies be returned to the United States for burial. He added that the Nicaraguan government had invited Powell and Parker to come to Nicaragua to claim the bodies of their sons.

Late this evening, U.S. Embassy officials reported that they have sent a note to the Nicaraguan government asking for its assistance in identifying the two Americans. The U.S. officials said they have sent for dental records of both men to be used in that process and they expected the documents to arrive Thursday.

Of the three bodies recovered from the crash, two were extensively burned. One of the bodies is thought to be that of a Nicaraguan rebel, Mario Pozo.

D'Escoto said Parker requested that the Nicaraguan government try to identify which body was that of his son in case he chooses to have the body returned to the United States.

"He was very grateful," said D'Escoto. According to D'Escoto, Parker said he had not been called by any representative of the U.S. government or by any representative of Civilian-Military Assistance, the group with which his son had traveled to Central America.

D'Escoto, a Maryknoll priest, said he spoke with Rose Powell, "extending our condolences to her as human beings, Christians and revolutionaries."

"What is important here isn't if these men are CIA agents," said D'Escoto. "What is important is that the activity in which they were involved could not have been carried out without the knowledge and consent of the CIA."

D'Escoto again insisted that the Reagan administration was responsible for the attack by three airplanes and the helicopter on a Sandinista Army training base, that killed three children and one adult.

"For Mr. Reagan might is right," said D'Escoto. He accused the United States of using "brute force" against the Sandinista government.

D'Escoto also said that while U.S. governments in the past had taken legal action against persons involved in private military ventures, the Reagan administration had allowed Civilian-Military Assistance to operate with impunity. He said "an exception to the law" had been made because the men were fighting to help overthrow the Sandinista government.

"Thousands of Nicaraguans have died," said D'Escoto, "and now two Americans die and you see an interest and a concern that wasn't there before."

D'Escoto said the deaths of the two Americans might make the U.S. public more critical of Reagan administration policy toward Nicaragua.