Rosalynn Carter, in a dramatic move intended to demonstrate the Carter administration's "deep commitment" to human rights, met unexpectededly today with two American missionaries who said they were beaten and jailed by Brazilian authorities last month.

"I have listened to their experience and I sympathize with them," Mrs. Carter said after the 15-minute meeting in the U.S. consulate here. "I have a personal message from them to take back to Jimmy."

A U.S. Official here said Mrs. Carter had agreed to the meeting after discussing it by telephone with President Carter.

It was considered sufficient that Mrs. Carter, who is on a goodwill tour of several Latin American countries took the opportunity to meet with the missionaries. Their ease has attracted international attention, and relations between the United States and Brazil have been strained over it and other human rights issues.

In the first Brazilian reaction to the meetings, which interrupted tMrs. Carter's rest visit here, the official responsible for investigating the incident said that he does not think that the gesture would affect U.S.-Brazilian relations.

Jose Moura Caalcanti, governor of the Pernambunco State, noted that Mrs. Carter had behaved "cordially" during her visit to Brazil so far and he said he doubts she would do anything "disagreeable" to the government. Recife is the capital of Pernambunco and, with 1.4 million people, the largest city in the relatively backward Northeast.

The missionaries are the Rev. Lawrence Rosebaugh, 42, Of Milwaukee, a priest of the Oblates of Mary Immaculate; and Thomas Capuano, 24, of Altamont, N.Y., a Mennonnite lay worker.

They were arrested here May 15 as they were pushing a cart, gathering discarded vegetables at an outdoor market to make soup for the poor people in a section of this sprawling city.

Police accused the two missionaries of associating with delinquents and having improper identification cards, but they were never charged with a crime.

Friends of the two told the U.S. consulate here about their detention, and American officials secured their released. On June 1 the U.S. government sent an "expression of concern" to Brasilia about the case, and Gov. Cavalcanti has launched an investigation by a police committee.

Conceding that there has been a delay in telling U.S. authorities about the arrest, Cavalcanti insisted: "But the fact that the two men were dressed as beggars and did not look like the photographs on their ID cards and had difficulty explaining their situation to the police could have happened in any civilized city in the world."

After their meeting with Mrs. Carter, Capauno said: "She really came across as sincere," adding that he thought she would take the President "not just out message, but the message of all those still suffering in that jail cell."

Mrs. Carter said she had decided to meet with the missionaries before her news conference in Brasilia yesterday, in which she declined to comment on their case. Asked then if her lack of response was a "cop out," she replied, not at all. She said she had discussed human rights extensively with Brasilian leaders, adding, "I am not avoiding the issue."

In March, Brazil canceled a military pact with the United States and rejected $50 million in loan credit because of a State Department report citing Brazil among countries violating human rights.

The report was mild, and U.S. officials traveling with Mrs. Carter have said that Brazil's record on human rights has improved and is now better than those of many other countries.

Today, however, the missionaries, who have worked among the poor in Brazil for 2 1/2 years, said, "Here there are flagrant violations of human rights."

Capauno told reporters, "I felt myself being turned into an animal. You could hear cries, groans of people getting beaten." He said he and Rosebaugh were in a cell, 10-feet wide and 25 feet long that contained 34 men all naked.

"A terrible stench was constant, the stench of human excrement, human sweat," he said. "There were wall-to-wall bodies. When it came to lie down, there was no room to lie down."

The prisoners were fed about 30 grams of manioc flour, a staple of the local diet here, and "a piece of meat the size of a quarter. When you eat it, it's gone, and then you scrape up crumbs from the floor."

Rosebaugh said he saw "one person forced to go down on his knees and licked grain on the floor with his tongue like a dog." He said the man was forced by a fellow prisoner, whom the police had made a leader.

Earlier, Mrs. Carter said on the flight to Recife that she was "really pleased" with her discussions with President Ernesto Geisel in Brasilia yesterday.

She said both governments had "misperceptions" on the issues of human rights and nuclear nonproliferation.

She declined to discuss specifics on the issues, particularly U.S. opposition to Brazil's plan to buy nuclear reprocessing equipment from West Germany, but she said, "I am very encouraged about the fact that there (are) specific things that we can now pursue, some understandings that we have that we didn't have before."