CEDAR RAPIDS, Iowa (Reuters) - Peregrine Financial Group Chief Executive Russell Wasendorf Sr. pleaded guilty in an Iowa courtroom on Monday to embezzling more than $100 million from customers of his futures brokerage, lying to regulators to cover his tracks, and mail fraud.

Wasendorf, 64, agreed to plead guilty to the charges earlier this month after confessing in July to stealing from clients for nearly 20 years.

Wasendorf, who has been in jail since being arrested in July for lying to regulators, will remain behind bars while a judge assesses whether he is a flight risk. He previously had been set to be released after the hearing Monday, but prosecutors argued he should stay in jail.

(Reporting By Ryan Schlader; Writing by Tom Polansek; Editing by Gary Hill)