The 28-year-old, who was released by Rotherham at the end of last season, has reportedly attracted a host of interest in recent weeks.
"I spoke to him and he came down to the area last week. He is somebody we like and somebody who knows the league very well," Knill told the club's official website.
"He's played for Barnsley and Rotherham, and we've put an offer to him. We are in negotiations with Dale and we will see where that goes."
Tonge joined Rotherham from Barnsley in 2007.