Mob associate Louis "Bent Finger Lou" Monacello pleaded guilty yesterday to plotting an assault on reputed mob underboss Martin Angelina.

Monacello, 43, appeared before Philadelphia Common Pleas Court Judge Charles J. Cunningham 3d during a brief hearing in which he admitted that he paid an associate to arrange to have Angelina beaten.

Under a plea agreement, he was sentenced to five years' probation that will include nine months of house arrest.

The plot was set in motion in the summer of 2008 when Monacello and Angelina had clashed over the collection of gambling and loan-sharking debts, according to law-enforcement sources familiar with the investigation.

Monacello's guilty plea yesterday came about a month after he pleaded guilty to gambling and obstruction of justice charges in Delaware County Court.

Both cases stemmed from a Pennsylvania State Police investigation dubbed "Operation Delco Nostra."

Monacello, described as a key associate of jailed mob leader George Borgesi, was one of 16 defendants charged in an investigation into mob-linked gambling and loan-sharking. Most of the defendants have pleaded guilty.

The plot to have Angelina beaten was one of the more bizarre twists in the Delco Nostra probe, built in part around conversations secretly recorded by Frank "Frankie the Fixer" DiGiacomo.

DiGiacomo, 47, has been described as a collector and sometime enforcer for Monacello. Late in 2007, he began cooperating with authorities and recorded dozens of conversations for state police.

In June and July 2008, according to details made public at a preliminary hearing in January, DiGiacomo recorded several conversations in which Monacello discussed the assault on Angelina.

At first, DiGiacomo said, Monacello talked about having Angelina killed. Later he changed his mind, saying, "Forget killing him. I want him beat up really bad."

DiGiacomo said Monacello agreed to pay $2,000 to DiGiacomo, who said he would find someone to carry out the assault.

One of the tapes played at the hearing in January included Monacello's counting out a $1,000 payment in $20 bills.

The tapes of those conversations and the cash were part of the evidence to support the charges.

During yesterday's hearing, Monacello pleaded guilty to one count of criminal solicitation to commit aggravated assault.

Under a plea agreement worked out with Chief Deputy Attorney General Erik Olsen, Monacello will begin serving the sentence imposed by Cunningham only after he has completed an 111/2-to-23-month sentence pending in Delaware County on the gambling and obstruction of justice charges.

He is scheduled to surrender to begin serving that sentence on Jan. 5.

Dressed in a business suit, shirt and tie, the always dapper Monacello declined to comment as he left the fifth floor courtroom except to say, "Happy holidays."

His lawyer, Robert Mozenter, told Cunningham before sentencing that Monacello "wants to get this behind him."

Mozenter said Monacello had suffered a financial loss and emotional distress because of his involvement in the Delco Nostra case.

"He made a mistake," the lawyer said. "He was on the fringe of a life he probably shouldn't have been involved in."

Monacello's two guilty pleas - in Philadelphia and Delaware County - have short-circuited DiGiacomo's debut as a trial witness.

DiGiacomo has been living in protective custody since the Delco Nostra arrests in July 2008.

In addition to working with the state police, DiGiacomo acknowledged in open court that he had contacted the FBI before he began cooperating.

Why he decided to cooperate has never been disclosed. And whether he will surface as a federal witness could not be determined.

Borgesi and his uncle, reputed mob boss Joseph Ligambi, remain two targets of an ongoing federal racketeering investigation.

Information gathered by the state police and the Attorney General's Office in the Delco Nostra case and in a more recent illegal video poker machine investigation could figure into that federal probe, several law enforcement sources say.

Contact staff writer George Anastasia at 856-779-3846 or ganastasia@phillynews.com.