The reputed underboss of the New England mob has pleaded guilty to federal bribery charges in a plea deal that will send him to prison for six years.

Carmen "The Cheeseman" DiNunzio pleaded guilty Wednesday to bribing an undercover FBI agent posing as a state highway department official in an attempt to win a $6 million contract on the Big Dig highway project.

DiNunzio is expected to plead guilty next week to separate state gambling and extortion charges.

Prosecutors have agreed to wrap both cases together under one plea agreement and to recommend a sentence of six years in federal prison. Sentencing was scheduled for Sept. 24.

Authorities say the 51-year-old DiNunzio has been underboss of the New England branch of the Mafia since 2004.