The Blues head coach also revealed contingency plans are already in place should the wing pair depart.
During the close season, The News has revealed both wide men are likely to depart Fratton Park this summer.
If the duo were to leave, it would end an attacking combination that has contributed 81 goals and 46 assists over the past three seasons.
Unsurprisingly, that makes up a sizeable percentage of Pompey’s attacking threat.
As a result of those impressive statistics, Cowley explained how such performances will always attract suitors from higher divisions.
For the time being, though, both remain on the Blues’ payroll and reported for duty when Pompey returned for pre-season training on Monday.
Meanwhile, the Fratton Park boss has adopted a pragmatic stance on their futures, with both players having just one year left on their current deals.
Cowley told The News: ‘The situation is the same as it was this time last year. Ultimately, Ronan is a Pompey player and I put Marcus Harness in the exact same bracket.
‘They’re both players who have performed exceptionally well for this football club for a consistent period of time.
‘They both score and create goals on a regular basis and as a consequence there’s always going to be interest in players of their ability.
‘It’s pretty well known they have a year left on their contracts and as a football club we’re open minded (about potential interest).
Harness is currently preparing for a fourth season at Fratton Park after the club took up an option on his contract at the end of last season.
It’s a move that allows the club to protect their asset and potentially receive some much-needed funds if their valuation of the 26-year-old is met.
The Blues will also loathe to see Curtis walk away for nothing at the end of the season, after they plucked him from Derry City in 2018 for a reported £100,000.
There’s a chance both will still be around when Pompey kick-off the new season on July 30.
However, Cowley knows anything can happen between then and now – and has carefully identified replacements if moves materialise and the offers appeal.
He added: ‘Unless you are Manchester City, Liverpool, Chelsea and Manchester United, all of the other 88 clubs’ players are for sale at the right price.
‘Certainly for clubs in League One, that’s the reality and what we have to do is make sure if any of our players were to leave: firstly, it’s for the right price; secondly, it’s on our terms; and, thirdly, we’ve done our due diligence and preparation to make sure we can replace those players.’