But the Blues boss admitted a repeat of his form from the first half of the season will see more eyes on the attacking talent.
Cowley believes the 25-year-old is heading towards a Republic of Ireland breakthrough, after bagging 10 goals to date this term.
Blackburn have been among the sides to show interest in the £750,000 arrival from Burton Albion in 2019, although it’s understood the Championship promotion chasers aren’t currently pursuing a deal.
Cowley played down news of second-tier interest in Harness, who he sees as a big part of his plans over the second half of the campaign.
He challenged the man who’s now made 118 Pompey appearances to deliver more end product to boost the prospects of his side - and his own future.
And Cowley believes personal landmarks look certain to arrive in terms of an international call-up, if Harness shows his worth.
Cowley said: ‘There’s naturally interest in a lot of our players.
‘But there’s been no formal bids, offers or even conversations actually (over Harness).
‘It definitely has (been a season where Harness’ standing has risen), absolutely without a doubt.
‘I was speaking to (Republic of Ireland assistant manager) Keith Andrews about him on Wednesday, actually.
‘He’s doing great and I definitely see an international call-up for Marcus.
‘That boy can be whatever he wants to be.
‘I think he’s had a really good season.
‘Our aim for Marcus now is to have as good a second half to his season as the first half.
‘If he does that, we will all benefit from that - both Marcus and obviously the club.’
Harness sees his three-year deal come to a close at the end of the campaign.
Pompey possess an option to extend that agreement by an 12 additional months, paving the way for them to protect their asset.
Cowley sees nothing getting in the way of the Blues actioning the clause, to ensure a man who has now become the most valuable player they possess remains.
He added: ‘I would have thought so (the option will be taken on his contract), I definitely would’ve thought so.
‘It will definitely be coming with the strongest of recommendations from me.’
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