Dr. Edmund Pellegrino, president of Catholic University, announced his resignation yesterday, saying he preferred to teach and do research rather than raise money almost full time.

Pellegrino, 62, a physician and expert on medical ethics, has been president of the financially squeezed university for the last three years.

He said he will leave July 1 to take a post as a professor of medicine and ethics at another university, although he said he hadn't decided yet which of three offers to accept.

"Next fall Catholic University will be starting a major fund-raising campaign for about $50 million that will run at least five years," Pellegrino said in an interview, "and the president will have to spend almost all his time on fund-raising. I am 62 years old, and it does not seem proper for me to make a commitment of that magnitude. I'd like to spend time on scholarly activities."

At a meeting with faculty members late yesterday afternoon, Pellegrino strongly denied campus rumors that he was leaving because of conflict with the university's board of trustees or its chancellor, Catholic Archbishop James A. Hickey of Washington.

"This was not a casual decision or one done in panic," Pellegrino said. "I talked with the board of trustees last July and they asked me to think about it." He said he told the board last Saturday that he definitely would resign.

Both Hickey and board Chairman Philip M. Hannan, the archbishop of New Orleans, issued statements warmly praising Pellegrino and expressing regret at his departure.

Faculty members interviewed yesterday also praised Pellegrino as a decisive leader who had made major changes in the college administration and adopted an austerity policy that kept the university budget in the black after many years of deficits that had been covered by the sale of university land. Several said it was unfortunate Pellegrino was leaving after only three years.

"It's the best for him," said David McGonagle, an assistant professor of Greek and Latin. "It would have been better if he could stay and help to carry out the programs he started. The change to new leadership will certainly slow things down."

Hannan said a search committee was being formed to find a new president who would take office as soon as Pellegrino leaves.

"Dr. Pellegrino is a man with extraordinary experience and extraordinary talent," Hannan said, "and we told him we would prefer that he continue. At the same time we did not want to deprive him of any opportunity to use his talents in the way he thought best."

Hannan said Pellegrino told him that one factor in his decision to turn full-time to teaching and medical research was the death of his 34-year-old son from acute heart disease last January.

"I think every doctor who has engaged in medical research and suffers a loss like that feels an extra impulse to do research," Hannan said.

Before going to Catholic University as its second lay president in almost 100 years, Pellegrino had been the first president of the Yale-New Haven Medical Center and a professor of medicine at Yale. Earlier, he had helped develop new medical schools at the University of Kentucky and the State University of New York at Stony Brook.

Pellegrino had also founded a journal of medicine and philosophy, which he continued to edit while serving as Catholic University's president. In Washington he continued to teach part time at the medical school at Georgetown University.

Catholic University, which has about 2,900 undergraduates and 5,000 graduate students, does not have a medical school.

"I've never been a full-time administrator," Pellegrino sasid yesterday. "The board of trustees knew that when they hired me . . . As long as I felt I was able to do all the things I wanted to and keep up my scholarship, I could continue as president. But if the fund-raising time had to increase and there was a conflict, I would have to make a choice."

"One is mortal," Pellegrino continued, "and when one gets to 62, one becomes sensitive to that. I think perhaps resigning as an administrator to do teaching and research would be the best way now to serve my fellows and society."