NEW YORK — Disgraced financier Bernard Madoff's longtime auditor is expected to plead guilty next week in a cooperation deal, federal prosecutors said today in a letter to a judge.

Prosecutors wrote in the letter to U.S. District Judge Alvin K. Hellerstein that accountant David Friehling was expected to plead guilty at a conference on Tuesday.

In the letter, signed by Assistant U.S. Attorney Lisa A. Baroni, prosecutors said they wanted to notify the court so it could provide notice to victims of Madoff's multi-billion-dollar fraud that the plea hearing will take place.

They said Friehling will enter the plea to revised charges that accuse him of securities fraud, investment adviser fraud, making false filings with the Securities and Exchange Commission and obstructing or impeding the administration of the Internal Revenue laws.

The charges carry a potential prison term of up to 108 years in prison, though substantial cooperation with prosecutors can result in leniency.

Authorities say if Friehling had done his job, Madoff's financial statements would have shown his company owed billions of dollars to customers and was insolvent.