The US Patent and Trademark Office has issued a final rejection of one of the five patents at issue in NTP's long-running case against BlackBerry maker Research In Motion.

The final rejection was posted on the USPTO's Web site for the NTP-held patent, which covers a system for sending e-mails over a wireless network to a mobile device. The USPTO has already issued nonfinal actions rejecting the claims in four out of the five NTP patents in question, but a final rejection is required before the appeals process can begin.

Contacted on Wednesday, NTP's lead counsel, James Wallace of Wiley, Rein & Fielding, said he had not reviewed the final action and therefore could not comment. NTP has the right to appeal any final rejection notice to a three-judge panel at the USPTO, and can file further appeals at the federal-court level.

RIM issued a statement confirming it had received the final action and said it expects the rejections to withstand future NTP appeals.

NTP, a patent holding company, successfully sued RIM for patent infringement and won an injunction, stayed pending appeal, to halt most sales of RIM's BlackBerry wireless e-mail device and service in the United States.

While the case has worked its way through the court system, the USPTO began reexamining the validity of NTP's patents.

NTP has said it plans see the full reexamination process through, which could take years, because it has the ability to appeal the decisions through the courts.

RIM and NTP are scheduled to argue the remaining portions of their patent dispute on Friday in a courtroom in Richmond, Virginia. The presiding judge in the case, US District Court Judge James Spencer, will decide whether NTP is entitled to an injunction against the sale and support of BlackBerry wireless e-mail devices in the US, a prospect that has the fiercely loyal BlackBerry community worried.

RIM shares were up 46 cents in midday trading at US$74.61.

CNET News.com reporter Anne Broache and Reuters contributed to this report.