Research in Motion (RIM), maker of the BlackBerry, gained some ground on Wednesday in long patent war as the U.S. Patent and Trademark Office issued a final rejection of one of five disputed patents owned by NTP.

NTP, a closely held patent holding company, has successfully sued Canadian firm RIM for infringement of its patents in 2003. An injunction was issued that would have shut down most sales and service of the Blackberry's e-mail device in the United States. RIM, however, has said that it plans to release a software workaround that would allow the service to continue to operate.

While the lawsuit has worked its way through the court system, the U.S. Patent Office began reexamining the validity of NTP's patents. On Wednesday the patent office's action marked the first "final" rejection of one of the patents at issue although the agency has previously issued "non-final" rejections of all five of the patents.

RIM said later in the day that the latest decision and previous rejections have been based on "multiple grounds" and "are expected to withstand all future appeals" by NTP.

Even the final rejection of the patents would not put an end to the lawsuit. This battle could take years as NTP has said it plans to see the full reexamination process through because it has the ability to appeal the decision. "The validity of the patents is not affected by preliminary PTO office actions," NTP said in a statement issued on Wednesday.

On Friday, the presiding judge in the case, U.S. District Court Judge James Spencer, will hold a hearing to consider NTP's request to go forward with an injunction that would shut down most sales of RIM's BlackBerry wireless e-mail device and service in the United States.