Prosecutors sought to keep secret their reasons for postponing former D.C. Council Chairman Kwame Brown's sentencing because disclosure "could impede ongoing investigations," court documents released Tuesday show. A judge agreed Monday to delay the sentencing hearing, but had refused to keep the rationale from public view.

Under the terms of his plea deal with prosecutors, Brown, who pleaded guilty in June to a felony bank fraud charge, pledged to assist authorities in ongoing investigations.

But prosecutors said Brown's assistance to them has not concluded and telling the public of his continued cooperation could hinder their efforts.

"Although the cooperation provision in the plea agreement is public, the extent and timing of any potential cooperation are not," prosecutors wrote in a court filing. "If such information were made public at this time, it could impede ongoing investigations by alerting persons suspected of engaging in criminal conduct of ongoing law enforcement activity and other information known to law enforcement."

U.S. District Court Judge Richard Leon, who is overseeing the federal component of the case against Brown, rejected the request to keep the reasons for the delay secret, saying the government had "failed to satisfy the court of its necessity."

Brown, who was to have been sentenced on Sept. 20, will instead appear before Leon on Nov. 13.

Under his plea deal, Brown faces up to six months in prison. Leon could opt for a harsher sentence of up to 30 years in prison, but such a ruling is unlikely because of federal sentencing guidelines.

The extent of Brown's cooperation could also impact his sentence, authorities said.

Brown resigned hours after prosecutors charged him with bank fraud on June 6, and he pleaded guilty two days later. In court, Brown acknowledged that he lied about his income to secure two loans, one of which he used to purchase a boat named "Bullet Proof."

Prosecutors also charged Brown with a local campaign finance violation: "aiding and abetting" cash expenditures of more than $50 from an account linked to his campaign.

That charge, a misdemeanor, carries up to six months behind bars.

A D.C. Superior Court spokeswoman said Brown's sentencing in that court would also be postponed.