The U.S. government has inserted itself in a high-stakes patent fight over the popular BlackBerry device, saying it wants to make sure federal workers won't be cut off from mobile access to their e-mail.

The Justice Department filed a "statement of interest" earlier this week to explain how the U.S. government, with as many as 200,000 BlackBerry users, could be harmed if a federal judge in Virginia issues an injunction against Research In Motion Ltd. to stop selling the device and accompanying e-mail service.

If the judge issues an injunction, "it is imperative that some mechanism be incorporated that permits continuity of the federal government's use of BlackBerry devices," the filing said.

The patent dispute with NTP Ltd. has heated with its return this week to the U.S. District Court for the Eastern District of Virginia — nicknamed the "Rocket Docket" for its speedy resolution of civil cases.

And RIM may have more reason to be concerned. In a status hearing Wednesday, Judge James R. Spencer appeared impatient to wrap up the long-running suit brought by NTP, which convinced a jury in 2003 that the technology behind the BlackBerry infringes on its patents.

The judge immediately dashed one of RIM's hopes. Spencer said it was unlikely he'd delay proceedings to wait for a re-examination NTP's patents by the U.S. Patent and Trademark Office, which recently issued preliminary rulings questioning their validity.

"I don't run their business and they don't run mine," Spencer said, asserting that he had spent enough time on the suit and intended to move swiftly on key issues.

Spencer, who issued an injunction against RIM after the 2003 jury verdict, but stayed it pending appeals, could rule before Thanksgiving on whether a $450 million settlement deal reached earlier this year is valid.

RIM says it is. NTP says it was never finalized.

The government filing by Paul J. McNulty, U.S. Attorney for the Eastern District of Virginia, said "there does not appear to be a simple manner in which RIM can identify which users of BlackBerries are part of the federal government."

But James H. Wallace Jr., an NTP attorney, called McNulty's filing "highly misleading and inappropriate."

Wallace said NTP has promised several times that an injunction would not apply to any government or emergency personnel in the United States, and said it would not be difficult for wireless carriers to identify such users.

McNulty said one way to ensure continued e-mail service for government employees would be to create a database of their devices. He suggested the court delay consideration of the injunction for at least 90 days, given the potential expense and complexity involved in inventorying those BlackBerries.

The filing included an estimate that anywhere from 50,000 to 200,000 federal employees use BlackBerry devices, which allow employees to retrieve and send e-mails when away from their office computers.