ROME — The FBI and Italian police said they had broken up a global heroin and cocaine trafficking ring Tuesday after stumbling upon a fledgling alliance between a Calabrian Mafia group and associates of New York's notorious Gambino crime family.

Twenty-four arrests were made in Italy and the United States after a two-year operation that relied on both wiretaps and an American undercover agent named by investigators as "Jimmy," who is said to have infiltrated the Gambinos and fooled Italians into believing he was a heroin dealer. Seventeen of the arrests were made in Italy and seven in the United States.

Those arrested in the U.S. were arraigned before a federal magistrate in Brooklyn. The men, some of them suspected of being members of the Gambino and Bonanno "families," were listed as using various street aliases such as "Lello," "Freddy," and "Charlie Pepsi."

The coordinated sting halted the planned shipment of more than a ton of cocaine from Latin America to Italy in liquid form, smuggled with help from Mexican cartels in coconut and pineapple cans, law enforcement officials said. They put the street value at $1 billion.

Speaking at a news conference in Rome, U.S. and Italian officials said the mob alliance was also planning to smuggle heroin into the United States, encouraged by the revival of the drug, which now is cheaper than cocaine. Its resurgence was highlighted early this month when Oscar-winning actor Philip Seymour Hoffman was found dead in his New York apartment, apparently from a heroin overdose.

The reported transatlantic team-up rekindled ties between American and Italian organized crime syndicates, which date to the "Pizza Connection" trafficking of drugs by U.S. mob groups and Sicily's infamous Mafia families in the 1970s and '80s.

Three decades on, the Gambino associates forged ties with the rising 'Ndrangheta crime group in Calabria, in the toe of Italy, which has supplanted the Sicilians in the international drug trade. The group is a trusted partner of South American cartels and is renowned for its tightknit blood ties.

"The international trafficking of drugs is almost monopolized now by the 'Ndrangheta," Italian anti-Mafia investigator Raffaele Grassi said Tuesday.

In New York, U.S. Atty. Loretta E. Lynch called the 'Ndrangheta "an exceptionally dangerous, sophisticated, and insidious criminal organization with tentacles stretching from Italy to countries around the world."

Officials said the Mafia alliance was forged at a meeting in Brooklyn.

"What we see here is an attempt by the 'Ndrangheta to gain a foothold in the New York area. We stand ready to prevent the 'Ndrangheta from gaining that foothold," said Asst. U.S. Atty. Marshall Miller.

George Venizelos, the FBI's assistant director in the New York City field office, said U.S. agents became involved after picking up signs that 'Ndrangheta members in Italy were working with the Gambino operation in the United States.

"Little did they know there was an ongoing collaboration between the FBI and the Italian National Police to investigate and identify their scheme," he said.

Gennaro Semeraro, chief of police of Reggio Calabria, said the 'Ndrangheta had initially been suspicious of "Jimmy," the American undercover agent who made trips to Calabria, "but he worked well and eventually he entered into their confidence."

The traffickers planned to use the port of Gioia Tauro in Calabria, which is also a staging post for chemical weapons being shipped from Syria for destruction.

The 15-count U.S. grand jury indictment alleged that some of the defendants had worked with Mexican drug cartels in Guyana, in South America, in the cocaine smuggling operation. There also were allegations, from undercover FBI officials wearing secret recording wires, that three of the defendants sold more than a kilogram of heroin to one agent, and that a sawed-off shotgun and silencer were sold to another agent at a meeting at the Royal Crown Bakery in Brooklyn.

In addition, in conversations picked up on Italian wiretaps, the FBI said, defendant Raffaele "Lello" Valente of Brooklyn bragged about assembling a crew of "well-armed men" in New York whose "base of operations was as secure as Ft. Knox."

Valente also allegedly talked about his religious devotion to St. Michael the Archangel — in Christian theology, Satan's foe in heaven — as his "patron saint." And he is accused of telling fellow Italian defendant Andrea Memmolo to wear "a special ring as a sign of pride and mutual recognition" between the two crime outfits in the two countries.

If convicted, the seven defendants in New York could be sentenced to 10 years to life in prison with no parole.

richard.serrano@latimes.com

Special correspondent Kington reported from Rome and Times staff writer Serrano from Washington.