A Russian court sentenced a Norwegian man to 14 years in jail for spying on Tuesday (April 16).

The verdict could strain relations between Moscow and its NATO-member neighbor.

Frode Berg, a retired guard on the Norwegian-Russian border, pleaded not guilty to spying for Norway.

He does admit he handled sensitive material about nuclear submarines on behalf of Norwegian authorities.

But he says he had no idea he was involved in espionage.

Berg, who was arrested more than a year ago, won't appeal the verdict and plans instead to request a pardon from President Vladimir Putin.

(SOUNDBITE) (English) BERG'S LAWYER, ILYA NOVIKOV, SAYING: "Mr Berg expects the Norwegian government will make any necessary diplomatic efforts to secure his presidential pardon and release by diplomatic channels." Last week, Putin seemed to leave the door open to a pardon.

Asked about that possibility he said he'd wait for the outcome of the trial and, quote, "we'll take a look at what we can do." Norway's foreign ministry didn't comment on the verdict, but it said it was working to bring Berg back to Norway.