Owen's late close-range volley brushed off James' head before flying over the crossbar as Pompey narrowly avoided only their third home Premier League defeat of the season.
James' amazing intervention was the only major talking point of a dour affair.
Portsmouth, chasing a club record fifth successive Premier League home win, felt they should have been awarded a first-half penalty.
Kanu's volley was well blocked by Newcastle defender Steven Taylor, but replays showed the ball bounced back off Taylor's outstretched right arm.
Referee Phil Dowd waved away Pompey's furious appeals, including those of manager Harry Redknapp who had seen the incident replayed on a television in the home dugout.
Portsmouth were playing their first home game since last weekend's FA Cup semi-final triumph over West Brom at Wembley.
There was a definite flatness about their play and only the in-form Jermain Defoe looked like getting on the scoresheet.
Defoe should have scored early in the second half when he was picked out by Niko Kranjcar's left-wing cross, but put a free header wide from eight yards.
Defoe has netted eight goals in seven games since joining Pompey from Tottenham in January.
But for the heroics of Newcastle goalkeeper Steve Harper, the England striker would have been celebrating a ninth.
Newcastle were committed up field after winning a corner when Defoe picked up the ball on the edge of his own penalty area.
Defoe exchanged passes with Sulley Muntari before unleashing a low right-foot shot from the edge of the penalty area.
Harper flung himself across his line before producing a brilliant fingertip save to turn the ball wide of the right-hand post as a low-key games ended goalless.