The Magpies agreed a fee with Portsmouth and the player travelled to Tyneside for a medical and to discuss personal terms on Friday.
Williamson has not played a single first-team game for Portsmouth after a summer move from Watford and will inevitably take some time to adjust, even if he is thrown straight into the Newcastle starting line-up.
Hughton: “In all honesty I’ve kept out of the politics of why it didn’t happen last week.
“I’m under the impression they’re working very hard on it and we’re confident it’s going to happen. I just want the player here. I hope we’re close to resolving it. We were disappointed it didn’t go through a couple of days ago and we’re hopeful something will happen very soon.
“This is a lad that did very well at Watford last season. He was on our radar last season and in the summer and got a big move to Portsmouth. Unfortunately he has not played the number of games he would like but must have been doing well to get that move in the first place.
“He is a big lad and he is the right age. There is still development in him and from what we’ve been led to believe, he will relish the opportunity to come here.”
Newcastle offered £975,000 for him last week.