O’Neill described Ireland’s first-half showing as “explosive” although it took until the opening moments of the second period for Norwich playmaker Wes Hoolahan to fire the Irish into a deserved lead, only for Clark’s intervention to ensure spoils were shared.
Maximum points would have been a huge tonic for Ireland in a group which also includes Belgium and Italy, although the manner of his players’ performance proved a comfort for O’Neill.
“It’s a massive disappointment because we dominated the game and played brilliantly,” said O’Neill.
“This was a winnable game for us with the way we performed. I am immensely proud of the players. They were explosive in the first half, they looked accomplished and they look as if they’ve grown into international football.”
Derby’s Jeff Hendrick rattled the Swedish crossbar in the first half but Ireland had to wait until the 48th minute to take the lead as Hoolahan directed a crisp half-volley beyond goalkeeper Andreas Isaksson.
But Sweden turned up the heat and levelled on 71 minutes as Clark headed a low cross from Zlatan Ibrahimovic past a stranded Darren Randolph.