Aaron Ramsey injury: Arsenal manager Arsene Wenger confirms midfielder has encountered 'difficulties' and will not be available to face Tottenham in Sunday's north London derby

Welshman has been out since Boxing Day with a thigh injury

Arsenal midfielder Aaron Ramsey goes down injured with a thigh strain in win at West Ham (GETTY IMAGES)

Arsenal manager Arsene Wenger has revealed that Aaron Ramsey has encountered "difficulties" in his recovery from a thigh injury, and will not be available to face Tottenham Hotspur in the north London derby on Sunday.

Wenger claimed last week that the Welshman, the Gunners' outstanding performer this season, would return for the fixture at White Hart Lane, having been out since Boxing Day after injuring his thigh in the 3-1 win at West Ham on Boxing Day. He was originally set to be sidelined for a month, but suffered a setback in training in January. Now it appears that his return to the first-team will have to wait.

"We have had to defer his comeback to full training a little so he is not available," Wenger said on Thursday.

"He is having difficulties in the final stages of his rehab. It looks to be short-term."

The man signed to deputise for Ramsey, Kim Kallstrom, has a chance of finally making his Arsenal debut on Sunday. The Swedish midfielder signed for the club on loan until the end of the season on transfer deadline day, despite a back injury. Wenger says that Kallstrom and second-choice striker Yaya Sanogo should be ready for the match.

"Kallstrom joins the normal training group today and Sanogo too," Wenger revealed.

"I will have to decide if Kallstrom is OK to be in the squad on Sunday. I will see how he looks. It is not impossible."

Left-backs Kieran Gibbs and Nacho Monreal have a "good chance" of being available. Gibbs has a fitness test on Friday.

"Kieran Gibbs has a test tomorrow but I am hopeful that Nacho Monreal will be fit. They both have a good chance," Wenger added.

It was reported on Wednesday that Mesut Ozil played on for 35 minutes with a hamstring injury in the 1-1 Champions League draw at Bayern Munich on Tuesday and will be out for six weeks, but Wenger says he still does not know the severity of the problem.

"He is out. I don’t know for how long but it is a hamstring injury. There are scans going on."