O'Neill saw his side compete well, and perhaps edge, the first half, only for Havard Nordtveit's deflected effort to send the visitors in with a 1-0 lead. Northern Ireland were not as lively in the second period and as they grew tired in the closing stages Norway pressed home their advantage with goals from Tarik Elyounoussi and Espen Ruud.
"I'm disappointed with the result, you can't get away from that," he said. "It's disappointing to lose two late goals when we were pushing to get something out of the game. I thought the scoreline was slightly harsh on us."
He added: "It's very difficult be analytical so soon after the game. I'll look at the game again in the cold light of day and I'm sure I'll find plenty of positives."
Lively performances from Dean Shiels and Shane Ferguson - who both started after O'Neill brought them in from two years in the cold - were two obvious high points.
O'Neill added: "In the first half we did a lot of good stuff, played well and got a lot of possession. Dean had a good 90 minutes dropping into the hole I thought. I thought Shane did extremely well too. He was very bright every time he was in possession and worked very hard in terms of the shape of the team."
O'Neill will have to wait until June 2 for his next game as national boss, a trip to Amsterdam to face Holland.
He admits such limited contact with his squad will take some getting used to, but is looking forward to the clash.
"We don't have a game for three months now and that's a long time to carry a defeat around with you, but unfortunately that's what I'm going to have to do," he said. "It's very difficult, there's no getting away from that, but that's what it's all about and it's a challenge I have to deal with.
"The next game is away to Holland, which is a difficult game. It'll be a big challenge but we have to prepare for difficult opposition because we have Russia and Portugal (in our World Cup qualifying group)."
Source: PA
Source: PA