Irvine has been a free agent since March when he departed Hull City and has been training with Kewell’s League Two side for the past week, leading to speculation that the 27-year-old could join the Latics permanently.
However, Irvine told The World Game he won’t be ending his 10-month spell away from the professional game by signing with Oldham.
“It’s just for fitness,” he said.
“Harry has been great letting me come in to top my levels up before I make a decision in January.”
The midfielder has been linked with the likes of Championship clubs Sheffield Wednesday and QPR in the past few months.
The former Burton Albion and Celtic man last played a competitive match of football in early March for Hull City.
Irvine has earned 34 caps for the Socceroos since making his debut in 2013.
Kewell confirmed that his compatriot won’t be signing for Oldham.
“I would love to say more, but no for Jackson, he’s been a little unfortunate,” he told the club website.
“He’s had a couple of offer but right at the last moment because of the COVID stuff, they fell through and he’s found himself in a little bit of limbo.
“It’s not a nice feeling as a footballer so, obviously, knowing him and the professional he is, he asked (to train with the Oldham) and I said I’d be happy to because what he brings is that extra bit of quality.
“As much as we’re helping him, he’ll help us. He helps some of the players, the players get on well with him they can learn from him and give them vital information I can’t give them, especially in certain positions.
“As I said, we’re here to help him out and get him fit and hopefully he can move onto bigger and better things because we need him back, definitely for Australia.”
Earlier this month former Australian international Robbie Slater urged the likes of Irvine to quit Europe and return home to play in the A-League.
Ex-Socceroo Kewell took over at the Latics in August.
On Boxing Day the League Two outfit went down 2-1 to Harrogate Town.
Under Kewell Oldham sit 14th in the 24-team competition with eight wins, two draws and 10 defeats from 20 matches.
