Tomorrow’s clash with Cheltenham Town at the Kassam Stadium is the last of the loan deals for Cox, Jake Forster-Caskey and Daniel Boateng.
It will definitely be the final games for Forster-Caskey and Boateng, who will return to Brighton and Arsenal respectively.
But the U’s are very keen to keep Swindon Town midfielder Cox, who has been excellent in the wins over Exeter City and AFC Wimbledon in the past week.
A solution will need to be found this week to ensure he can play in Saturday’s FA Cup third-round tie against Sheffield United and Wilder is hopeful of getting an answer before tomorrow’s game.
The United boss said: “There are three parties involved – us, Lee Cox and Swindon – so it has to be right for everyone.
“Lee has done well and is in our thoughts about extending.
“It will definitely be sorted, possibly leading up to the Cheltenham game we’ll know which direction we’'re going in.”
Cox has said in the past he was enjoying his spell at United after failing to get regular football with Swindon last season.
And the 22-year-old is clear about where he sees his future.
He said: “I’d love to stay at Oxford and hopefully Cheltenham isn’t my last game for them and there’s a lot more to come.
“I’m not part of the gaffer’s plans at Swindon and I’ve been given a chance here to play football with a very good team.
“I’ve felt part of it since going to America in pre-season.”
“There are some good games coming up and you can see there’s a turnaround in the club.
“We want to get up that table, I’m determined to help the club get up there.”