President Clinton said yesterday that political considerations "played no role" in his decision to grant clemency to 16 Puerto Rican nationalists, as he tried to quell criticism of a move that has bedeviled the first lady's Senate campaign.

In a five-page letter to Rep. Henry A. Waxman (D-Calif.), Clinton said the Puerto Rican militants "were serving extremely lengthy sentences" and deserved to be freed because "our society believes . . . that a punishment should fit the crime."

Clinton had made such statements before, but yesterday's letter provided more details and his most extensive explanation to date. It did little to appease disgruntled members of Congress, however, including some usually reliable Clinton loyalists such as Waxman.

Waxman, the ranking Democrat on the House Government Reform Committee, read the president's letter aloud near the beginning of the panel's hearing yesterday on the clemency offer for members of the FALN terrorist group. But after emotional testimony from victims of FALN violence and tough Republican criticism, Waxman indicated that he, too, disagreed with the president's decision to grant clemency.

"I probably wouldn't have," Waxman said. "Whether he is right or wrong, so far the judgment of my colleagues in Congress is that his judgment is wrong."

Several Republicans and witnesses at the hearing said the president's decision sent the wrong message about U.S. policy on terrorism. Clinton, they said, would bear some responsibility the next time a terrorist group, emboldened by the clemency, attacked innocent Americans. They also said it was hypocritical for Clinton to speak at the United Nations about the world's need to combat terrorism and nuclear weapons, only days after releasing the FALN members.

"I pray to God this will not start a new reign of terror," said Rep. Dan Burton (R-Ind.), chairman of the Government Reform Committee.

Clinton announced on Aug. 11 that he had offered conditional clemency for 16 FALN members. None had been convicted of crimes directly linked to violent injuries, although other FALN members were responsible for 130 bombings that killed six people and maimed others.

Republicans quickly accused Clinton of trying to build support among Puerto Rican voters for his wife's Senate bid in New York. Hillary Rodham Clinton eventually said the clemency offer should be withdrawn because the FALN members had not renounced violence.

In fact, the president's offer was predicated on the renouncing of violence, which the 14 who accepted the offer agreed to within a few days. Some Democrats said the first lady's comments added to the public confusion about the issue and played into Republican portrayals of the FALN members as dangerously violent.

In his letter, the president said the 16 members, "while convicted of serious crimes, were not convicted of crimes involving the killing or maiming of any individuals. For me, the question, therefore, was whether the prisoners' sentences were unduly severe and whether their continuing incarceration served any meaningful purpose."

Nine of the 16 FALN members were convicted of seditious conspiracy, armed robbery and various firearms offenses. Each had served 19 years in prison.

Yesterday's committee hearing was marked by testimony from victims of FALN violence and tough talk from a senior FBI official, who made it plain that Clinton had overruled the agency's views.

"They are criminals, and they are terrorists, and they represent a threat to the United States," said Neil Gallagher, the FBI's assistant director for national security. The administration had blocked Gallagher from testifying at similar hearings last week.

While Justice Department officials declined comment on what they had advised the president--citing the president's legal right to confidential advice on such matters--the committee released a draft letter from FBI Director Louis J. Freeh saying the FBI strongly opposed the early release.

"The FBI has consistently advised the Department of Justice (DOJ), in writing, that the FBI was opposed to any such pardon and/or commutation of sentences for any of these individuals," Freeh wrote in the draft, addressed to House Judiciary Committee Chairman Henry J. Hyde (R.-Ill.). Freeh noted that few of the prisoners had expressed remorse for their acts and warned that "any such pardon of the currently incarcerated terrorists would likely return committed, experienced, sophisticated and hardened terrorists to the clandestine movement."

CAPTION: Reps. Henry A. Waxman, left, and Dan Burton appear at hearing at which Waxman read a letter from the president.