The beleaguered president of the AFL-CIO, John Sweeney, was dealt another blow yesterday as the leader of a politically potent firefighters’ union signaled that his support for the federation chief is eroding.

In a letter to Mr. Sweeney, the general president of the International Association of Fire Fighters, Harold Schaitberger, resigned his position as chairman of the public affairs committee of the AFL-CIO’s executive council. Mr. Schaitberger complained that he was kept out of the loop on Mr. Sweeney’s plans to release a detailed restructuring plan for the federation.

The AFL-CIO distributed the 26-page document last Thursday, and Mr. Sweeney held a conference call with reporters that day, touting the blueprint as a key step in reversing labor’s shrinking membership base and political might.

Mr. Schaitberger, who is known as a skilled lobbyist, said he met with Mr. Sweeney twice last week, but the AFL-CIO chief said nothing about the imminent release of the reform plan.

“John, I can’t view this incident as merely an ‘oversight.’ Not giving me, at a minimum, a heads up… was not only disappointing, it was also very telling,” Mr. Schaitberger wrote in the letter, which was dated April 29.

In response to press questions, Mr. Sweeney issued a written statement yesterday that did not address the substance of Mr. Schaitberger’s complaints. “We are deeply sorry that President Schaitberger is resigning as chair of the Public Affairs Committee,” Mr. Sweeney wrote. “We value his leadership and insight, and believe that the union movement needs him to continue to lead in this and other areas.”

While the dispute may seem petty, it comes as Mr. Sweeney is struggling to quell a serious rebellion among the federation’s member unions. In March, five large unions, including the Service Employee International Union and the Teamsters, forced a vote on a plan that could have forced the national federation to cut its staff in half. Mr. Sweeney defeated that proposal, but the upstart unions won roughly 40% of the vote, which is allocated based on the unions’ membership numbers.

During that showdown, Mr. Schaitberger and the firefighters stood by Mr. Sweeney. However, the chilly tone of Mr. Schaitberger’s latest missive suggests that he has soured on Mr. Sweeney, who faces re-election at a union convention in July. A spokesman for Mr. Schaitberger said he was traveling yesterday and unavailable to comment.