Arsène Wenger has confirmed Mesut Özil and Aaron Ramsey will miss Sunday's derby at Tottenham Hotspur through injury, although the Arsenal manager hopes Kim Kallstrom, his only signing during the midwinter transfer window, may be fit enough to be included in the squad.

Arsenal have had to postpone Ramsey's return to competitive action as he struggles in the final stage of his rehabilitation from the thigh injury sustained at West Ham on Boxing Day. The Wales midfielder had long since targeted the visit to Spurs – the first of a difficult sequence of Premier League fixtures that may define the club's title challenge – for his comeback and had resumed first-team training at the beginning of last week.

There have been minor setbacks in the period since, which may also rule him out of the trip to the leaders, Chelsea, on 22 March. More realistic may be the midweek visit of Swansea City on 25 March. "We have had to defer his comeback to full training a little, so he is not available [at Spurs]," Wenger said. "He is having difficulties in the final stages of his rehab. It looks to be short-term."

Özil was forced off at half-time in the Champions League last-16 second leg tie at Bayern Munich on Tuesday with a hamstring injury and, although the club continue to assess the extent of the injury, early signs suggest the Germany international will miss at least a month. "He is out," Wenger said. "I don't know for how long but it is a hamstring injury. There are scans going on."

Arsenal hope to have their record signing available again for the FA Cup semi-final against Wigan Athletic at Wembley on 12 April.

While the club are already resigned to being without Jack Wilshere for six weeks with a hairline fracture of his foot, they have been encouraged by Kallstrom's potential availability for the weeks ahead. The Sweden international arrived on loan from Spartak Moscow in January, despite suffering from a fractured vertebra in his back at the time. The Russian club have met his wages during his rehabilitation, which has taken him back to his native Sweden to visit the former England doctor, Leif Sward, for treatment.

The hope is he will be available to make his belated Arsenal debut in the key period ahead. "Kallstrom joins the normal training group on Thursday and [Yaya] Sanogo too," Wenger said. "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. Kieran Gibbs has a test on Friday but I am hopeful that Nacho Monreal will be fit. They both have a good chance."