The ruling followed similar decisions on several other patents held by Arlington, Va.-based NTP Inc., which is seeking an injunction against continued operation of the BlackBerry service in the U.S. by Research In Motion Ltd.

But Todd Kort, a Gartner Inc. analyst, said it could take a year or so for the PTO to formally invalidate all of NTP's patents. Because the federal judge overseeing NTP's lawsuit against RIM has said he won't hold up the case while the patents are re-examined, Kort expects the PTO's preliminary rulings to prompt NTP to bargain harder for an upfront financial settlement that would prevent any BlackBerry service disruptions.

Last week, though, NTP officials vowed to contest the PTO's rejection of the company's patent claims. "We're not rolling over on this and playing dead," said NTP attorney James Wallace Jr. via e-mail. "This is going to be reversed."

With a Feb. 24 hearing looming on NTP's injunction request, the patent-holding firm and RIM filed memorandums in U.S. District Court in Richmond, Va. The U.S. Department of Justice also weighed in with a brief arguing against an injunction.

In its memorandum, NTP demanded a payment of nearly US$126 million from RIM to cover lost licensing fees.