Visto has signed a licence for the wireless e-mail patents held by NTP, increasing pressure on Visto main rival RIM.

RIM is currently locked in a closely watched courtroom struggle with NTP over whether its BlackBerry system infringes on those same patents.

NTP has now obtained licences from Visto, Good Technology and Nokia for patents that describe a system of sending e-mail messages wirelessly to handheld devices, aka push e-mail. RIM is facing an injunction in the US on the sale of BlackBerry devices after failing, through several avenues of appeal, to overturn a jury's verdict that the company has infringed NTP's patents.

Financial terms of the Visto/NTP licensing deal were not disclosed.

Analysts believe RIM will settle its legal dispute with NTP rather than face an injunction, which could shut down the BlackBerry service in the US. Earlier this year, the companies announced a $450 million settlement but it fell through. This time around, it could cost RIM twice that amount to keep the BlackBerry service going, according to analysts.

RIM has been reluctant to settle before the preliminary findings of the US Patent and Trademark Office which may invalidate NTP's patents altogether . But the process of obtaining a final ruling could take several years to wind its way through the appeals process. Judge James Spencer of the Virginia court ruled two weeks ago that the patent case would proceed without waiting for the PTO's decision.