Goal revealed last month that the 29-year-old was in talks over a new deal that would see him tied to the club until 2017.
|7/2||Arsenal are 7/2 with BetVictor to win the title|
Wenger told reporters: “We are in the process of extending Mertesacker’s contract. "He has one-and-a-half years left - there is plenty of time."
Mertesacker was signed by Arsenal for £10 million from Werder Bremen in August 2010 and initially struggled to adapt to the frenetic pace of the Premier League.
Gradually, however, he has adapted and grown to become an integral part of Wenger’s plans and has ousted captain Thomas Vermaelen as the club’s first choice centre-back.
Mertesacker, who scored the winning goal in Germany’s 1-0 win over England at Wembley on Tuesday, is almost certain to return to the starting line-up when Arsenal entertain Southamtpon on Saturday having missed the defeat at Old Trafford a fortnight ago with a flu bug.