Research in Motion has settled its patent dispute with NTP. The BlackBerry maker has agreed to pay $612.5m which includes a perpetual licence on the patents at the centre of a prolonged legal battle between the two firms.

The judge presiding over the case was expected to rule in NTP's favour and order a shutdown of the wireless email service in North America.

NTP co-founder Donal Stout said in a statement: "We are pleased to have reached an amicable settlement with RIM. We believe that the settlement is in the best interests of all parties, including the US government and all other BlackBerry users in the US."

The two parties reached an agreement in March 2005 to settle the case for $450m, but this later fell apart.

A jury found in 2002 that RIM infringed on NTP-owned patents covering an email system on mobile devices.

The US Patent and Trademark Office, meanwhile, has started to re-examine the NTP patents and has already invalidated several.

A decision on the remaining patents is expected soon, although the procedure could take years. A possible invalidation would affect the settlement.

Even though RIM faces the risk of buying a licence for patents that could be invalidated, the litigation was scaring away customers and affecting revenues, according to Kevin Burden, programme manager for mobile devices and services at analyst firm IDC. 

"This is probably money well spent. It's a boatload of money for patents that may not be worth anything, but it's worth it if it removes the cloud over RIM's future," Burden told vnunet.com.