The US patent office has issued a final rejection of one of the patents at the centre of a long-running wrangle between patent-holder NTP and Research In Motion, maker of the Blackberry wireless device.
On Friday, US courts are set to hear NTP's case for an injunction against RIM that threatens to shut down the US Blackberry network.
The possibility of a shutdown prompted RIM to issue a workaround designed to keep the Blackberry service running in the event of an injunction, although industry analysts warned that the move should be seen as a negotiating tactic.
But during the lengthy legal battle, the US Patent and Trademark Office began the process of re-examining NTP's patents.
Now, in a boost to RIM, it has issued a final rejection of one of five patents at the heart of the legal dispute. All five patents have already had "non-final" rejections.
In a statement, RIM said: "The rejections from the Patent Office were all based on multiple grounds, required the unanimous agreement of three senior patent examiners and are expected to withstand all future appeals by NTP."