Blackberry devices are used by three million people in the US

Research In Motion (RIM) is embroiled in a legal dispute with technology firm NTP, which says the Blackberry has infringed its patents.

Blackberry could have been forced to shut down its mobile e-mail service in the US immediately.

But Judge James Spencer said he would consider an injunction in the future.

No ruling

He said that RIM had infringed NTP's patents and that he would rule on an injunction as "soon as reasonably possible" but did not indicate when he might do so.

RIM's shares closed up 6.5% at $74.05 after the firm escaped immediate sanction.

The BBC's North America business correspondent, Guto Harri, said many Americans welcomed the development as if hearing good news about their health or their family.

Switching off the US service would have caused misery for more than three million users, he said.

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RIM claims to have a software patch that would enable its handheld e-mail devices to work even if the ruling goes against it.

Legal experts said they expected the judge would press both sides to settle the dispute out of court.

"He certainly wants them to settle," Steve Maebius, a patent lawyer with Foley & Lardner, told Reuters.

"He is giving them one more chance to do that."

Addicted

Canada-based RIM said recently that it was negotiating with NTP, but described the US firm's offer to license the disputed technology as "untenable".

The tussle between the two companies dates back to 2002, when patent-holding company NTP successfully sued RIM in a lower court.

The two firms agreed a tentative settlement last year but the agreement subsequently collapsed.

Earlier this month, the US government asked a federal judge to hold off from a possible shutdown of the Blackberry service, because of the system's popularity among key government employees.