The 30-year-old called time on his 44-cap Wales career in August 2018, saying he wanted to focus on club football and dedicate more time to his family.
But in November the striker revealed he’d held talks with Ryan Giggs about a potential return.
The 2019/20 campaign has been the most prolific of Robson-Kanu’s career.
As well as putting in a string of outstanding displays for Slaven Bilic’s side, the has also netted 10 goals – the first time he has ever reached double figures.
And Wales favourite Hartson – who scored 14 goals in 51 appearances for his country – has welcomed Robson-Kanu’s decision to make himself available again.
“Hal’s put himself forward again and I think that’s great,” Hartson said.
“He deserves credit for that, he wants to help and be a part of it.
“He’s been scoring goals and pivotal to what Slaven Bilic has been doing at West Brom.
“He was getting a run of games after a few injury problems, and I think it’s wonderful for Ryan to have options.”
Giggs appeared to cast doubt on Robson-Kanu returning for this month’s friendlies against Austria and the United States - now cancelled because of the coronavirus outbreak.
That seemed to end Robson-Kanu’s hopes of making a dramatic return at this summer’s European Championship, four years after he etched his name in Welsh football folklore by scoring a wonder goal in the Euro 2016 quarter-final win over Belgium.
But the possibility that Euro 2020 could be postponed and potentially rescheduled for the summer of 2021, could work in the 30-year-old’s favour by allowing him more time to reintegrate into the squad.
“My only issue - and I think Ryan might be thinking the same - is that he’s got the likes of Daniel James, Harry Wilson and Tom Lawrence in forward positions, as well as Gareth Bale of course and David Brooks to come back from injury,” Hartson continued.
“Ryan’s been trying to nurture and bring through some of the younger ones to become future Welsh stars.
“He might feel that bringing Hal back in might hold their progress.
“But Hal’s a quality player and made himself a fans’ favourite by scoring that great goal against Belgium at the Euros in 2016.
“We want good players and you can’t have enough good players.
“He’s got good experience, but Ryan has to decide whether it halts the progress of one of his younger players.”