The band's frontman made the comment during an appearance with Tory leader David Cameron at a secondary school in Cheshire.
Asked if he would work with Williams again, the Daily Record quotes him as saying: "We'll see. I think it's inevitable one day we'll get back together."
Barlow was launching a singing competition for pupils at the school called 'School Stars'.
Williams left Take That in 1995 but speculation has been rife that he will eventually return to the band.