The acquittal of mob boss Anthony "Tony" Salerno on charges he helped rig the elections of Teamster Presidents Roy Williams and Jackie Presser strikes a crippling blow to government plans to take over the nation's largest union, law enforcement sources say.

Salerno was convicted Wednesday of racketeering in the construction industry but was acquitted with two other reputed mob figures on charges of fraud in Williams' and Presser's elevations to the Teamsters presidency in 1981 and 1982.A federal law enforcement source, speaking on condition of anonymity, said the acquittal by a federal court jury in New York on the Teamster-related counts is "a serious setback."

In light of the verdict, he said, the government will have to conduct a "major re-evaluation" of bringing a civil suit to oust Presser and other top officials in the 1.6-million-member Teamsters union and replace them with a court-appointed trustee.