“I cannot support a man who’s a co-founder of an organization that engaged in over 120 bombings,” Mr. O’Neill said of Mr. López Rivera, adding that he considered him a terrorist, “based on his actions, based on the fact that he was the co-founder of that group and what he was convicted of.”

Several police organizations have also announced that they will not march in the parade, including the Hispanic Society, the largest organization of Hispanic officers.

The parade, considered one of the largest Hispanic-centered events in the city, announced several weeks ago that it would honor Mr. López Rivera. It said he would march at the head of the parade and be declared a National Freedom Hero, a designation never given by the parade before.

The controversy contained echoes of a dispute in 1983, when the St. Patrick’s Day Parade was roiled by the naming of an Irish Republican Army supporter, Michael Flannery, as grand marshal. Cardinal Terence Cooke, who opposed violence in Northern Ireland, pointedly did not receive him at the steps of St. Patrick’s Cathedral, as is customary.

Senator Daniel Patrick Moynihan and the former Gov. Hugh L. Carey boycotted that parade, as did a score of high school bands. However, Gov. Mario M. Cuomo, Mayor Edward I. Koch and Senator Alfonse M. D’Amato all marched.

Less than 12 weeks before that parade, on New Year’s Eve 1982, the F.A.L.N. detonated four bombs in New York City, seriously injuring three police officers.