Kenny Jackett has made no secret of his desire to strengthen his midfield options ahead of the League One kick-off.
And he has identified the 26-year-old as his fifth recruit of the summer.
It is understood the Blues favour a season-long loan for O’Keefe, who has fallen out of favour at the Championship club.
The midfielder spent the second half of last season on loan at MK Dons, scoring four goals in 18 appearances.
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Yet upon his return to the Bluebirds, his first-team chances have grown ever distant.
The former Crystal Palace man’s availability has alerted Jackett, who has been eyeing a fresh addition to his midfield.
Pompey have lost Michael Doyle, Amine Linganzi and Stanley Aborah from their League Two title-winning squad.
And while the new boss has strengthened in goal, defence and attack, a midfielder has so far eluded him.
The Blues’ recent recruitment plans have so far been hamstrung by a bulging squad and a necessity to remove players from the wage bill first.
It has prompted Gary Roberts and Michael Smith to be told they have no Fratton Park future – with takers desperately required.
In the meantime, the hunt has been on for likely midfield candidates, with O’Keefe emerging as a target.
Jackett had spoken of the one-out, one-in policy, but it remains to be seen whether the Tornante investment group’s expected takeover will allow that to be navigated around.
Michael Eisner, son Eric, and president and chief operating officer Andy Redman are currently in England with a view to finalising the £5.67m deal.
That is anticipated being sealed towards the end of the week – potentially in time for Saturday’s League One curtain-raiser against Rochdale.
In the meantime, Jackett continues to pursue O’Keefe, who played Premier League football during his days at Selhurst Park.
He totalled 51 appearances for the Eagles and scored on his top-flight bow in a 3-1 win over Sunderland in August 2013.
He later had a loan spell at Blackpool, before joining Cardiff for an undisclosed fee in January 2015.
During his first full season with the Bluebirds, O’Keefe made 27 outings, of which 25 were starts.
However, last term he was restricted to just nine appearances, before spending the remainder of the campaign on loan at MK Dons.
Jackett has opted to employ Carl Baker in the centre of midfield in Pompey’s past two friendlies.
The wideman has impressed in the new role alongside Danny Rose, while Ben Close and Adam May are options. But another midfield recruit remains the Blues’ priority.