The FBI agent who infiltrated the Gambino crime family (search) did it so effectively, he was nearly "made."

The 48-year-old unidentified agent became a "listed" member of mobster Greg DePalma's crew and was told last month he would be put up for promotion, sources said.

"Had we left him out on the street much longer, the Gambino family ranks would actually have increased by one," said Pasquale D'Amuro, head of the FBI's New York office.

Authorities said it was the deepest penetration of the mob since agent Joseph Pistone (search), posing as jewel thief Donnie Brasco (search), slipped into the Bonanno crime family 25 years ago.

The agent, a married man with children, "risked his life as a mole for the better part of two years," said U.S. Attorney David Kelley.

Sources said his role as a Gambino wiseguy began a couple of years ago when an FBI informant introduced him as an out-of-towner with access to stolen property.

The agent showered gifts on DePalma and the crew — including $5,000 watches, flat-screen TVs, jewelry, cars and cash — all property that previously had been seized by the feds.