Rudy Giuliani, a federal prosecutor who later became NYC Mayor, was unrelenting in his campaigns against New York's five Mafia families in the mid-1980s, and had formed ties with Italian prosecutors which raised the wrath of "boss of bosses" Salvatore "Toto" Riina who ordered a hit against the mob buster as reported by Nick Squires for The Telegraph:
The claims were made to Italian investigators this week by Rosario Naimo, a mafia "pentito" or supergrass, who was a member of Cosa Nostra and lived for years in the US. Naimo claims he was ordered by a Sicilian "man of honour" to transmit a message to the Gambinos, one of America's most notorious crime families. The message, from Riina, asked the Gambinos to assassinate Mr Giuliani, who had established a reputation for aggressive investigations into organised crime in New York.
Toto Riina is serving life terms for ordering the 1992 murders of Italian judges Giovanni Falcone and Paolo Borsellino in separate bomb attacks, and the imprisoned boss recently was caught on a wiretapped conversation calling for a renewed terror campaign against the state.
The Sicilian Mafia has long had deep ties with New York's Gambino family, and it remains inexplicable why the U.S. Treasury Department has not designated their alliance as a transnational criminal organization under Executive Order 13581 to freeze their assets and ban Americans from conducting any business with them.
Further reading that may be of interest: