An elderly and prominent Syrian rabbi from Brooklyn has pleaded guilty to laundering tens of thousands of dollars through a religious charity.

Saul Kassin, 89, rabbi of Congregation Sharee Zion in Brooklyn, the largest Syrian Sephardic synagogue in the US, confessed his crime to a federal court earlier this week.

He admitted that in 2007 and 2008 he used his charity, the Magen Israel Society, to launder money given to him by property kingpin Solomon Dwek, the son of a prominent Syrian rabbi. Under the arrangement, Kassin and his charity kept 10 per cent.

After Dwek was arrested in 2006 on unrelated bank-fraud charges, he co-operated with federal investigators and helped trap Kassin in a sting operation that resulted in the sensational arrests in 2009 of 44 people, including five Orthodox rabbis and several New Jersey politicians. The probe centered on the town of Deal, where many Syrian Jews have summer homes.

Some were charged with money laundering and corruption, while one man was accused of being a broker of black-market kidneys.

So far, 26 of those arrested have pleaded guilty, three have been found guilty, and two acquitted.

Under the deal between the prosecutors and Kassin, the rabbi is not expected to do prison time, although the charge carries a maximum penalty of five years in prison and a $250,000 fine. He agreed to forfeit $367,500 that the FBI seized from the charity. Sentencing will take place in July.

Kassin tried to speak his mind in court, reaching for an envelope where he appeared to have a speech written, according to one newspaper.

"I believe in the truth," he said, but the judge told him he was not allowed to talk. His lawyer, Gerald Shargel, said outside court that the rabbi didn't realise he had done anything illegal. "He's very trusting and he was duped by a scoundrel," Mr Shargel said.